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VectorPlot (vc) Resources

vcExplicitLabelBarLabelsOn
This boolean resource allows you control the labels that appear in the VectorPlot LabelBar explicitly. When set True, VectorPlot does not block the LabelBar resources lbLabelStrings and lbLabelAlignment. Therefore you can directly control both the contents of the LabelBar's label strings and their alignment with respect to the label boxes. When vcExplicitLabelBarLabelsOn is set False, VectorPlot sets both of these resources based on the current vector line labels and the value of the resource vcLabelBarEndLabelsOn. If you set this resource True but do not set the lbLabelStrings array resource, VectorPlot will set it for you one time. This allows you to get an initial set of strings as a starting point for any customization you want to perform.

Default: False

vcFillArrowEdgeColor
When vcMonoFillArrowEdgeColor is set True, this resource of type NhlTColorIndex sets a uniform color index for the edges of all filled vector arrows. If set to Transparent (-1), the edge line will not be drawn at all for filled vectors, assuming the fill color index is set to a value other than Transparent. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: Background

vcFillArrowEdgeThicknessF
This resource sets the thickness of the lines used to form the edges of filled vector arrows. The value acts as a multiplier of a (device-dependent) unit thickness. If vcFillOverEdge is set True, note that the edge will not fully appear unless it is drawn using thickness greater than 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 2.0

vcFillArrowFillColor
When vcMonoFillArrowFillColor is set True, this resource of type NhlTColorIndex sets a uniform fill color index for all filled vector arrows. If set to Transparent (-1), the arrow will not be filled at all and only the perimeter will be drawn. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: Foreground

vcFillArrowHeadInteriorXF
This resource specifies the distance from the point of the arrowhead of a filled vector arrow drawn at the reference length to the point where the arrowhead joins with the line extending to the tail of the arrow. The value represents a fraction of the value of vcRefLengthF. (See figure.) This distance is adjusted proportionally to the X component of the arrowhead size for all vector arrows. The value of vcFillArrowHeadInteriorXF is constrained to the range 0.0 through 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.33

vcFillArrowHeadMinFracXF
This resource specifies the X component of the arrowhead size for a filled arrow drawn at the minimum length, as a fraction of the component length specified by vcFillArrowHeadXF. (See figure.) If given the value 1.0, the arrowhead X component will be the same for all arrows in the plot, regardless of their length. The value of vcFillArrowHeadMinFracXF is constrained to the range 0.0 through 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.25

vcFillArrowHeadMinFracYF
This resource, when added to the minimum width value, specifies the Y component length of the arrowhead size for a filled arrow drawn at the minimum length, as a fraction of the component length specified by vcFillArrowHeadYF. (See figure.) If given the value 1.0, the arrowhead Y component will extend the same distance perpendicularly from the edge of all arrows in the plot, regardless of their length and width. This can be a useful resource to adjust to ensure that the points of even very short vector arrows remain visible. The value of vcFillArrowHeadMinFracYF is constrained to the range 0.0 through 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.25

vcFillArrowHeadXF
This resource specifies the distance from the point of the arrowhead of a filled vector arrow drawn at the reference length to its back tips along the centerline of the arrow. The value represents a fraction of the value of vcRefLengthF and determines the X component of the arrowhead size. (See figure.) If vcFillArrowHeadMinFracXF has the value 0.0, then the ratio of the X component of the arrowhead size to the arrow length will be invariant for all vectors in the plot. The value of vcFillArrowHeadXF is constrained to the range 0.0 through 2.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.36

vcFillArrowHeadYF
This resource specifies the perpendicular distance from one side of a filled vector arrow drawn at the reference length to one of the back tips of the arrowhead. The value represents a fraction of the value of vcRefLengthF and, when added to half the arrow width, determines the Y component of the arrowhead size. (See figure.) If both vcFillArrowHeadMinFracYF and vcFillArrowMinFracWidthF have the value 0.0, then the ratio of the Y component of the arrowhead size to the arrow length will be invariant for all vectors in the plot. The value of vcFillArrowHeadYF is constrained to the range 0.0 through 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.12

vcFillArrowMinFracWidthF
This resource specifies the width of a filled arrow drawn at the minimum length, as a fraction of the width specified by vcFillArrowWidthF. (See figure.) If given the value 1.0, all arrows in the plot will be drawn at the same width, regardless of their length. The value of vcFillArrowMinFracWidthF is constrained to the range 0.0 through 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.25

vcFillArrowWidthF
This resource specifies the width of a filled vector arrow drawn at the reference length as a fraction of vcRefLengthF. (See figure.) If vcFillArrowMinFracWidthF has the value 0.0, then the ratio of the arrow width to the arrow length will be invariant for all arrows in the plot. The value of vcFillArrowWidthF is constrained to the range 0.0 through 1.0. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: 0.1

vcFillArrowsOn
vcGlyphStyle overrides and eventually is intended to replace this resource. However, if you set vcFillArrowsOn and do not at the same time set vcGlyphStyle, you can use it to select between the LineArrow and FillArrow glyph styles. When set True, fill arrows are selected; when set False, line arrows are selected.

Default: False

vcFillOverEdge
If this boolean resource is set True, the perimeter outline of a filled vector arrow is drawn first, underneath the fill. In this case, the line must be drawn using a line thickness greater than 1.0 in order for the line to appear. The advantage of drawing the line underneath is that the full extent of the fill appears; when the line is drawn on top of the fill using a different color index, the fill color may be partially or completely obscured, especially for small vector arrows. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: True

vcGlyphOpacityF
Available in version 6.1.0 and later.

Sets the opacity of vector glyphs in a plot. Specify a floating-point value between 0.0 (completely transparent) to 1.0 (fully opaque).

Default: 1.0

vcGlyphStyle
This resource selects the style of glyph used to represent the vector magnitude and direction. There are four choices:
LineArrow
Vectors are represented using an arrow-shaped polyline pointing in the direction of the vector. The arrow length and head size may vary with the magnitude of the vector. Resources prefixed by vcLineArrow... have an effect when vcGlyphStyle is set to this value.
FillArrow
Vectors are represented using a polygon and possibly a polyline edge that point in the direction of the vector. The length, width, and various parameters affecting the head size and overall shape may vary with the magnitude of the vector. Resources prefixed by vcFillArrow... have an effect when vcGlyphStyle is set to this value.
WindBarb
Vectors are represented using a standard wind barb glyph, composed of a shaft parallel to the vector direction, and pennants and/or ticks spaced at even intervals along the shaft starting at the end nearest the direction from which the flow is coming. (For the purposes of the vcPositionMode resource, this end is the "tail" of the wind barb.) If the velocity is less than 2.5 in magnitude, a circle is drawn instead of the barbed shaft. Otherwise half ticks represent 5 units of magnitude, full ticks represent 10 units, and pennants represent 50 units. By convention, the units usually represent knots. The pennants are drawn using a filled polygon, while the ticks, the shaft, and the calm circle are all rendered with polylines. Unlike the other glyph styles, wind barbs maintain a basically uniform length for all magnitudes. Resources prefixed by vcWindBarb... have an effect when vcGlyphStyle is set to this value.
CurlyVector
Vector are represented using a curved polyline tangent to the instantaneous flow in the neighborhood of the grid point. A variably-sized arrowhead at one end of the line points in the direction of the flow. The path length of the curve may vary with the vector magnitude at the grid point location. CurlyVector mode is like LineArrow mode in that it is rendered using a polyline, and therefore resources prefixed by vcLineArrow... have an effect when vcGlyphStyle is set to this value. Unlike the other glyph styles, when vectors drawn with this style are colored, the color varies along the path length of the vector depending on the interpolated value of the magnitude or other scalar field at each step along the path.

This resource overrides and eventually is intended to replace the resource vcFillArrowsOn. vcFillArrowsOn can still be used to choose between line arrows and fill arrows, as long as you do not set vcGlyphStyle at the same time.

Default: LineArrow

vcLabelBarEndLabelsOn
When this boolean resource is set True and vcExplicitLabelBarLabelsOn is False, VectorPlot creates labels for the two ends of the LabelBar. The label at one end will be a string representation of a minimum value and at the other end will be a string representation of the maximum value. These values represent either a vector magnitude or, if vcUseScalarArray is set True, some other scalar value. Both strings will be formatted according to the format specification in effect for the other labels provided by VectorPlot to the LabelBar.

Default: False

vcLabelFontColor
If vcLabelsUseVectorColor is set False, this resource specifies the HLU color index used to draw the vector magnitude labels.

Default: Foreground

vcLabelFontHeightF
This resource specifies the NDC height of characters used for vector magnitude labels. The label font height scales with changes to the viewport width, unless you explicitly set vcLabelFontHeightF during the same call.

Default: <dynamic>

vcLabelsOn
If this resource is set True, VectorPlot will place labels representing the vector magnitude next to each arrow in the vector field plot. These labels are primarily intended as a debugging aid, since in order to avoid excessive overlap, you must typically set the label text size too small to be readable without magnification. For this reason, only a few resources are available to control the appearance of these labels. They are rendered using low quality text.

Default: False

vcLabelsUseVectorColor
If this resource is set True, VectorPlot draws the vector magnitude labels using the color of the corresponding vector. Otherwise the labels are drawn using the color index specified by vcLabelFontColor.

Default: False

vcLevelColors
The elements of this array of type NhlTColorIndexGenArray can be set using an array of color indexes, an array of named colors, or an array of RGB or RGBA values.

If vcGlyphStyle is set to LineArrow or CurlyVector and vcMonoLineArrowColor is False, this resource controls the color of the line-drawn vector arrows. If vcGlyphStyle is set to FillArrow, then this resource may control the fill and/or the edge color of the filled vector arrows, depending on the values of the resources vcMonoFillArrowFillColor and vcMonoFillArrowEdgeColor. If vcGlyphStyle is set to WindBarb and vcMonoWindBarbColor is False, this resource controls the color of the wind barb glyphs.

Each element of vcLevelColors specifies a color for vectors whose associated scalar data value is less than the corresponding element of the vcLevels array. Note that there is always one more color than there are vector levels. The first element of vcLevelColors specifies a color index for any vector with an associated data value less than the value of vcMinLevelValF. The highest currently used element of vcLevelColors specifies a color for vectors with associated data values greater than the value of vcMaxLevelValF.

When vcGlyphStyle is set to CurlyVector, the vectors appear multicolored with the color varying along the path length of the vector depending on the interpolated value of the magnitude or other scalar field at each incremental step.

Although backwards compatibility is for the most part maintained, beginning with version 6.1.0, this resource supports the new 32-bit color model, as follows:

If vcLevelColors is not set explicitly, its values are derived from the settings of vcLevelPalette and vcSpanLevelPalette, or, if vcLevelPalette is not set, wkColorMap and vcSpanLevelPalette. If vcSpanLevelPalette is True, the values are distributed evenly through the range of colors available from vcLevelPalette or wkColorMap. Otherwise, the values are sequential. If the color indexes are derived from vcLevelPalette the first color comes from element 0, whereas if they are derived from wkColorMap, the first color comes from element 2. This is because wkColorMap contains special elements (0 and 1) for the Background and Foreground colors, whereas the palette-type resources do not. If some but not all of the available elements of vcLevelColors are explicitly set, the remaining elements will be determined as if vcSpanLevelPalette has the value False.

For backwards compatibility, colors set based on wkColorMap remain indexed to the current color map associated with the workstation. Consequently, if the workstation color map is changed prior to drawing the plot, the color indexes will map into the new color map. In contrast, color indexes derived from the vcLevelPalette resource always refer to a specific color regardless of changes to wkColorMap.

Default: <dynamic>

vcLevelCount
A read-only resource set to the actual number of levels chosen during the level selection process.

Default: 16

vcLevelPalette
Available in version 6.1.0 and later.

This resource of type NhlTColorDefinitionGenArray allows you to set a color palette from which the values assigned to vcLevelColors are chosen.

You can set this resource to the string name of a predefined color map, an array of named colors, or an array of RGB or RGBA values. If you set vcLevelPalette using a predefined color map, it will have two fewer elements than if you set wkColorMap using the same color map. This is because the wkColorMap resource contains special elements (0 and 1) for the Background and Foreground colors, whereas the palette-type resources do not. Use vcSpanLevelPalette to indicate whether to span the full color palette or to simply use sequentially increasing values.

Default: None

vcLevelSelectionMode
This enumerated resource of type NhlTLevelSelectionMode provides four methods for selecting the levels used to color the vector arrows:
AutomaticLevels
Ordinarily this mode determines vector levels by picking a spacing value from a set of relatively "round" numbers scaled by powers of 10 to the range of the data. This set of numbers is as follows: 1.0, 2.0, 2.5, 4.0, 5.0. The number of levels chosen will be as close as possible to the value of vcMaxLevelCount without exceeding it. Once the spacing is chosen, the minimum vector level is set to the value of the least multiple of the spacing greater than the minimum data value. Likewise the maximum vector level becomes the greatest multiple of the spacing less than the maximum data value. Based on these values, VectorPlot sets the resources vcLevelSpacingF, vcMinLevelValF, and vcMaxLevelValF appropriately.

On the other hand, if you explicitly set the resource vcLevelSpacingF to a valid value greater than 0.0 and less than the range of the data, it will be used as the interval spacing. The minimum and maximum levels are calculated as before. If as a consequence, vcMaxLevelCount is less than the number of levels so specified, it will be set to the number of levels actually needed. However, if the choice of spacing causes the absolute maximum number of levels (currently 255) to be exceeded, VectorPlot will issue a warning message and recalculate the spacing as previously described.

In any case, VectorPlot sets the elements of the array resource vcLevels to the values of the vector levels chosen and the read-only resource vcLevelCount to the number of levels.

ManualLevels
ManualLevels mode bases the choice of vector levels on the values of the resources vcLevelSpacingF, vcMinLevelValF, and vcMaxLevelValF. Starting at vcMinLevelValF, vector levels are created at intervals spaced by the value of vcLevelSpacingF until vcMaxLevelValF is reached. The final vector level will always be vcMaxLevelValF. VectorPlot sets elements of the array resource vcLevels to the values of each vector level chosen and the read-only resource vcLevelCount to the number of levels. If the current value of vcMaxLevelCount is less than vcLevelCount, it is reset to the value of vcLevelCount. However, if the level count would exceed the absolute maximum number of levels, currently 255, VectorPlot issues a warning and chooses a new value of vcLevelSpacingF based on the value of vcMaxLevelCount.

If you choose ManualLevels selection mode when the VectorPlot object is created, and do not set vcMinLevelValF, VectorPlot will choose levels as if you had set AutomaticLevels mode. If you set vcMinLevelValF only, a default spacing is used, and the value of vcMaxLevelValF is determined as it would be for AutomaticLevels mode.

ExplicitLevels
This mode allows you to specify the value of each vector level by explicitly setting the contents of the vcLevels array. If you choose ExplicitLevels selection mode when creating a VectorPlot object, but do not specify the contents of the vcLevels array, VectorPlot will choose levels as if you had specified AutomaticLevels mode. Thereafter, when you set ExplicitLevels mode, VectorPlot uses the current contents of vcLevels, whether or not you set it explicitly.

If the number of elements in vcLevels exceeds the absolute maximum number of levels (currently 255), VectorPlot issues a warning and the mode defaults to AutomaticLevels. Note that VectorPlot always sorts the elements of vcLevels into a monotonically increasing sequence. After sorting, vcMinLevelValF is set equal to the value of first element of vcLevels, and vcMaxLevelValF is set to the value of the last element. vcLevelSpacingF is set to the average value of the spacing separating each level.

EqualSpacedLevels
For this mode, VectorPlot divides the range spanning the dataset minimum and maximum values into vcMaxLevelCount+1 equally spaced intervals. vcLevelSpacingF is set to the value of this interval. vcMinLevelValF is set to the value of the dataset minimum plus the value of vcLevelSpacingF. vcMaxLevelValF is set to the value of the dataset maximum minus the value of vcLevelSpacingF. This results in vcMaxLevelCount levels; therefore VectorPlot sets the read-only resource vcLevelCount equal to vcMaxLevelCount.

Default: AutomaticLevels

vcLevelSpacingF
When the vcLevelSelectionMode is ManualLevels or when the vcLevelSelectionMode is AutomaticLevels, and vcLevelSpacingF is explicitly set, vcLevelSpacingF determines the spacing between vector intervals. Otherwise, the VectorPlot object sets the value of vcLevelSpacingF based on the vector levels actually chosen. When the vcLevelSelectionMode is ExplicitLevels, vcLevelSpacingF will be set to the arithmetic average of the spacing between levels.

Default: 5.0

vcLevels
An array of floats containing values that determine the color of the vector arrows in the vector field plot. If vcScalarFieldData is valid and the resource vcUseScalarArray is set True, the level values are based on the scalar array data; otherwise the level values are based on the magnitudes of the vector elements in the vector field. If the vcLevelSelectionMode is ExplicitLevels, you may set these values yourself. Otherwise, the VectorPlot object sets the elements of this array.

Default: <dynamic>

vcLineArrowColor
When vcMonoLineArrowColor is set True, this resource of type NhlTColorIndex sets a uniform color index for all lines used to draw vector arrows. If set to Transparent (-1), the line color index will be constrained to the value Foreground (1). This resource has an effect only when vcGlyphStyle is set to LineArrow or CurlyVector.

Default: Foreground

vcLineArrowHeadMaxSizeF
Specifies a maximum length for the lines that form the point of the arrowhead of line-drawn vectors, as a fraction of the viewport width. Normally the arrowhead size is scaled proportionally to the length of the vector. This resource allows you to ensure that the arrowheads do not become excessively large for high magnitude vectors. If vcLineArrowHeadMinSizeF is set to the same value as vcLineArrowHeadMaxSizeF, all arrowheads in the vector plot will be drawn at the same size. Setting both resources to 0.0 will cause the arrows to be drawn without any heads at all. This resource has an effect only when vcGlyphStyle is set to LineArrow or CurlyVector.

Default: 0.05 (LineArrow), 0.012 (CurlyVector)

vcLineArrowHeadMinSizeF
Specifies a minimum length for the lines that form the point of the arrowhead of line-drawn vectors, as a fraction of the viewport width. Normally the arrowhead size is scaled proportionally to the length of the vector. This resource allows you to ensure that the arrowhead will remain recognizable even for very short vectors. If vcLineArrowHeadMinSizeF is set to the same value as vcLineArrowHeadMaxSizeF, all arrowheads in the vector plot will be drawn at the same size. Setting both resources to 0.0 will cause the arrows to be drawn without any heads at all. This resource has an effect only when vcGlyphStyle is set to LineArrow or CurlyVector.

Default: 0.005

vcLineArrowThicknessF
This resource sets the thickness of the line used to draw vector line arrows. The value acts as a multiplier of a (device-dependent) unit thickness. This resource has an effect only when vcGlyphStyle is set to LineArrow or CurlyVector.

Default: 1.0

vcMagnitudeFormat
The vcMagnitudeFormat resource is a string that specifies the printing format for vector field values according to the HLU Floating Point Format Specification scheme. This resource controls the formatting of any number representing VectorField data when used in a VectorPlot annotation.

Default: "*+^sg"

vcMagnitudeScaleFactorF
vcMagnitudeScaleFactorF is a read-only resource that contains the current scale factor that applies to annotations with numbers representing magnitudes in the VectorField data object. Multiplying the numbers in the annotations by the value of vcMagnitudeScaleFactorF gives the actual magnitudes the numbers represent. VectorPlot calculates its value based on the maximum vector magnitude, the current mode of the enumerated resource, vcMagnitudeScalingMode, and perhaps the value of vcMagnitudeScaleValueF. Its value may also be influenced by the number of significant digits specified by the format specification resource, vcMagnitudeFormat.

Default: 1.0

vcMagnitudeScaleValueF
The interpretation of vcMagnitudeScaleValueF depends on the value of the enumerated resource vcMagnitudeScalingMode. When vcMagnitudeScalingMode is set to ScaleFactor, values are divided by the value of vcMagnitudeScaleValueF to obtain the numbers appearing in VectorPlot object labels. If vcMagnitudeScalingMode is set to ConfineToRange, the vcMagnitudeScaleValueF represents an exclusive upper bound for the numbers used to represent the data values. For other values of vcMagnitudeScalingMode, the vcMagnitudeScaleValueF resource is ignored.

Default: 1.0

vcMagnitudeScalingMode
This resource of type NhlTScalingMode determines how numbers representing magnitudes in the vector field data are scaled when they appear in the annotations provided by VectorPlot. There are five choices:
ScaleFactor
The VectorPlot object divides the magnitude by the value of vcMagnitudeScaleValueF to obtain the number that appears in the label.
ConfineToRange
The VectorPlot object uses vcMagnitudeScaleValueF as an exclusive upper bound. A scale factor is selected such that the scaled maximum magnitude will be less than vcMagnitudeScaleValueF, but greater than or equal to vcMagnitudeScaleValueF divided by 10.0. As an example, setting vcMagnitudeScaleValueF to 100.0 would result in the number used to represent the scaled maximum magnitude falling in the range 10.0 to 99.999....
TrimZeros
The VectorPlot object selects a scale factor such that the number representing the scaled maximum magnitude will have the fewest possible extra zeros. If the maximum magnitude were 245000, for instance, it would scale to 245. If it were 0.000245, it would scale to 0.245. (The zero conventionally placed before the decimal point of a number less than 1.0 is not considered.)
MaxSigDigitsLeft
The VectorPlot object selects a scale factor such that the number representing the scaled maximum magnitude will have its rightmost significant digit directly to the left of the decimal point. The number of significant digits is determined by the format string resource, vcMagnitudeFormat.
AllIntegers
The VectorPlot object selects a scale factor such that the numbers representing the vector levels (as determined by examination of the values of the vcLevels array) are reduced to integers.
In each case, the scale factor selected is placed into the read-only resource, vcMagnitudeScaleFactorF.

Default: ScaleFactor

vcMapDirection
This resource controls whether the vector direction is mapped into the same coordinate space as the vector location, or whether it is rendered in a locally uniform cartesian coordinate space. This resource has an effect whenever a non-uniform transformation is in effect. These include most of the MapTransformation transformations and IrregularTransformation transformations. Also included are logarithmic transformations provided by the LogLinTransformation and even linear transformations when the X and Y unit sizes are different.

Default: True

vcMaxLevelCount
When the vcLevelSelectionMode is AutomaticLevels and vcLevelSpacingF is not explicitly set, VectorPlot picks a number of levels less than or equal to the current value of vcMaxLevelCount. If the vcLevelSelectionMode is EqualSpacedLevels, VectorPlot picks exactly vcMaxLevelCount levels. If vcMaxLevelCount exceeds the absolute maximum level count allowed by VectorPlot (currently 255), a warning is issued and the value is reset to this maximum. If vcLevelSelectionMode is ManualLevels or ExplicitLevels or AutomaticLevels with vcLevelSpacingF explicitly set, VectorPlot sets vcMaxLevelCount to the number of levels actually used if this number is greater than the current value of vcMaxLevelCount.

Default: 16

vcMaxLevelValF
When the vcLevelSelectionMode is ManualLevels, the value of vcMaxLevelValF, if set, determines the highest vector level. Otherwise, VectorPlot sets the vcMaxLevelValF to a value equal to highest vector level picked.

Default: <dynamic>

vcMaxMagnitudeF
This resource specifies a maximum magnitude for elements of the vector field. Vectors with magnitudes greater than this value will not be rendered in the vector field plot.

Default: 0.0

vcMinAnnoAngleF
NOT YET IMPLEMENTED.

Default: 0.0

vcMinAnnoArrowAngleF
This resource specifies the angle, in degrees, of the arrow used in the minimum vector annotation.

Default: 0.0

vcMinAnnoArrowEdgeColor
If vcMinAnnoArrowUseVecColor is set False, this resource specifies the HLU line color index used to render the arrow in the reference annotation. If vcMinAnnoArrowUseVecColor is set True, and either vcUseScalarArray or vcMonoLineArrowColor is True, the line color index is determined from the value of vcLineArrowColor. If vcMinAnnoArrowUseVecColor is set True otherwise, the line color index is determined based on the magnitude of the reference annotation vector and the vcLevelColors array resource.

Default: Foreground

vcMinAnnoArrowFillColor
If vcMinAnnoArrowUseVecColor is set False, this resource specifies the HLU fill color index used to render the arrow in the reference annotation. If vcMinAnnoArrowUseVecColor is set True, and either vcUseScalarArray or vcMonoFillArrowFillColor is True, the fill color index is determined from the value of vcFillArrowFillColor. If vcMinAnnoArrowUseVecColor is set True otherwise, the fill color index is determined based on the magnitude of the reference annotation vector and the vcLevelColors array resource. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: Foreground

vcMinAnnoArrowLineColor
If vcMinAnnoArrowUseVecColor is set False, this resource specifies the HLU line color index used to render the arrow in the reference annotation. If vcMinAnnoArrowUseVecColor is set True, and either vcUseScalarArray or vcMonoLineArrowColor is True, the line color index is determined from the value of vcLineArrowColor. If vcMinAnnoArrowUseVecColor is set True otherwise, the line color index is determined based on the magnitude of the reference annotation vector and the vcLevelColors array resource.

Default: Foreground

vcMinAnnoArrowMinOffsetF
This resource specifies the minimum amount of space between the minimum vector annotation arrow and the text on either side in units of the minimum annotation font height.

Default: 0.25

vcMinAnnoArrowSpaceF
This resource specifies the minimum amount of space reserved for the reference vector annotation arrow in units of the minimum annotation font height. More space may be used if the arrow extent (in units of the font height) plus twice the value of vcMinAnnoArrowMinOffsetF exceeds this value.

Default: 2.0

vcMinAnnoArrowUseVecColor
If this resource is set True, VectorPlot will base the coloring of the minimum arrow on the colors used to draw the vector plot arrows as follows: if coloring by magnitude is in effect (vcUseScalarArray and, depending on the value of vcGlyphStyle, the appropriate "mono" color flag is set False), then the color will be that assigned to vectors representing the magnitude of the minimum annotation vector; otherwise, the color index will be determined from the current values assigned to vcLineArrowColor and/or vcFillArrowFillColor. If vcMinAnnoArrowUseVecColor is False, then vcMinAnnoArrowLineColor and vcMinAnnoArrowFillColor control the color of the minimum annotation arrow.

Default: True

vcMinAnnoBackgroundColor
This resource sets the background color used to fill the box surrounding the vector minimum annotation. If you do not want the box to be filled at all, set vcMinAnnoBackgroundColor to Transparent (-1).

Default: Background

vcMinAnnoConstantSpacingF
Normally when vcMinAnnoFontQuality is set to High, VectorPlot draws the minimum vector annotation text using proportional spacing. Setting the vcMinAnnoConstantSpacingF to a value greater than 0.0 overrides this behavior. Instead, the distance from the start of one character to the next is computed by multiplying a single standard character width by the value of vcMinAnnoConstantSpacingF. When vcMinAnnoConstantSpacingF has a value between 0.0 and 1.0, characters will overlap. A value of 1.0 implies, on average, no space between characters, while values increasing from 1.0 cause the space between characters to grow. This parameter is ignored when vcMinAnnoFontQuality is not High. Values less than 0.0 result in an error and are replaced with the default value.

Default: 0.0

vcMinAnnoExplicitMagnitudeF
By default, the arrow in the minimum vector annotation is drawn at the size of the current VectorPlot minimum magnitude. However, if you set this resource to a value greater than its default value of 0.0, the size of arrow will reflect the vector magnitude represented by this value.

Default: 0.0

vcMinAnnoFont
This resource of type NhlTFont specifies the font used to render the vector minimum annotation.

Default: "pwritx"

vcMinAnnoFontAspectF
This resource determines the shape of the minimum vector annotation characters. Values increasing from 1.0 result in characters that appear thinner. Values decreasing from 1.0 make the characters appear wider. Values less than or equal to 0.0 result in a WARNING message and a restoration of the default value.

Default: 1.3125

vcMinAnnoFontColor
This resource specifies the HLU color index used to render vector minimum annotation text.

Default: Foreground

vcMinAnnoFontHeightF
This resource controls the height, in NDC units, of characters used in the text of the minimum vector annotation. The character width scales proportionally, unless you also modify the aspect ratio using the vcMinAnnoFontAspectF resource. The minimum annotation font height scales with changes to the viewport width, unless you explicitly set vcMinAnnoFontHeightF during the same call.

Default: <dynamic>

vcMinAnnoFontQuality
This resource of type NhlTFontQuality determines the quality of the font used to draw the VectorPlot vector minimum annotation.

Default: High

vcMinAnnoFontThicknessF
Sets the thickness of the line used to draw vector minimum annotation text. The value acts as a multiplier of a (device-dependent) unit thickness. This resource is ignored when the vcMinAnnoFont specifies a filled font (font indexes 21-22, 25-26, 29-30, and 33-37).

Default: 1.0

vcMinAnnoFuncCode
This resource of type NhlTCharacter sets the function code character for the minimum vector annotation strings.

Note: the default function code was a colon (:) in NCL Versions 6.0.0 and earlier.

Default: ~

vcMinAnnoJust
This resource of type NhlTJustification, after constraint to an appropriate value based on vcMinAnnoSide, sets the justification of the vector minimum annotation with respect to its base location. The PlotManager Location Control Model requires this resource to allow control of the vector minimum annotation consistent with other annotations.

Default: TopRight

vcMinAnnoOn
If this boolean resource is set False, VectorPlot will not draw the minimum vector annotation.

Default: True

vcMinAnnoOrientation
NOT YET IMPLEMENTED

This resource of type NhlTOrientation specifies whether the elements of the minimum vector annotation (two strings with an arrow representing a vector magnitude in between) are stacked vertically or placed side by side horizontally.

Default: Vertical

vcMinAnnoOrthogonalPosF
vcMinAnnoOrthogonalPosF sets the coordinate of the base location of the vector minimum annotation orthogonal to the current vcMinAnnoSide and directed away from the center of the viewport. The PlotManager Location Control Model requires this resource to allow control of the vector minimum annotation consistent with other annotations.

Default: 0.02

vcMinAnnoParallelPosF
vcMinAnnoParallelPosF specifies the coordinate of the base location of the vector minimum annotation parallel to the current vcMinAnnoSide and directed toward increasing NDC values. The PlotManager Location Control Model requires this resource to allow control of the vector minimum annotation consistent with other annotations.

Default: 1.0

vcMinAnnoPerimColor
This resource sets the HLU color index used to draw the perimeter of the vector minimum annotation.

Default: Foreground

vcMinAnnoPerimOn
vcMinAnnoPerimOn is a boolean resource that determines whether VectorPlot will draw an outline around the perimeter of the box surrounding the minimum vector annotation. If set False, no outline will be drawn.

Default: True

vcMinAnnoPerimSpaceF
vcMinAnnoPerimSpaceF determines the spacing, or margin, between the text of the minimum vector annotation and its edge as a fraction of current minimum annotation font height.

Default: 0.33

vcMinAnnoPerimThicknessF
This resource determines the thickness of the perimeter line around the vector minimum annotation. The value acts as a multiplier of a (device-dependent) unit thickness.

Default: 1.0

vcMinAnnoSide
This resource of type NhlTPosition determines where to place the vector minimum annotation in relation to the sides of the plot object. The PlotManager Location Control Model requires this resource to allow control of the vector minimum annotation consistent with other annotations. Its value determines a coordinate system origin and the direction of the positional resources vcMinAnnoParallelPosF and vcMinAnnoOrthogonalPosF. It also constrains the value of vcMinAnnoJust appropriately. There are four settings, which behave as follows, unless vcMinAnnoZone is set to one of the special zones (0 or 1):
Top
The PlotManager locates the vector minimum annotation relative to a line paralleling the top viewport boundary. vcMinAnnoOrthogonalPosF increases in the direction of increasing NDC Y-Axis values and is constrained to positive values. vcMinAnnoParallelPosF increases in the direction of increasing NDC X-Axis values. vcMinAnnoJust is constrained to BottomRight, BottomCenter, or BottomLeft.
Bottom
The PlotManager locates the vector minimum annotation relative to a line paralleling the bottom viewport boundary. vcMinAnnoOrthogonalPosF increases in the direction of decreasing NDC Y-Axis values and is constrained to positive values. vcMinAnnoParallelPosF increases in the direction of increasing NDC X-Axis values. vcMinAnnoJust is constrained to TopRight, TopCenter, or TopLeft.
Right
The PlotManager locates the vector minimum annotation relative to a line paralleling the right viewport boundary. vcMinAnnoOrthogonalPosF increases in the direction of increasing NDC X-Axis values and is constrained to positive values. vcMinAnnoParallelPosF increases in the direction of increasing NDC Y-Axis values. vcMinAnnoJust is constrained to TopLeft, CenterLeft, or BottomLeft.
Left
The PlotManager locates the vector minimum annotation relative to a line paralleling the left viewport boundary. vcMinAnnoOrthogonalPosF increases in the direction of decreasing NDC X-Axis values and is constrained to positive values. vcMinAnnoParallelPosF increases in the direction of increasing NDC Y-Axis values. vcMinAnnoJust is constrained to TopRight, CenterRight, or BottomRight.
If vcMinAnnoZone is set to 0, The PlotManager locates the vector minimum annotation relative to the viewport center. If vcMinAnnoZone is 1, the direction of the vcMinAnnoOrthogonalPosF is opposite to the specification given above. Also if the vcMinAnnoZone is either 0 or 1, vcMinAnnoJust is not constrained, and vcMinAnnoOrthogonalPosF may take on negative values.

Default: Bottom

vcMinAnnoString1
Specifies the string to use above or to the left (depending on the current value of vcMinAnnoOrientation) of the arrow in the minimum vector annotation. The string may contain function codes and/or substitution substrings.

vcMagnitudeFormat determines the format of all numbers related to the vector field, and all numbers, except for the number generated from the substitution substring $MSF$, are scaled by the value of vcMagnitudeScaleFactorF. vcScalarValueFormat determines the format of all numbers related to the scalar field, and all numbers, except for the number generated from the substitution substring $SSF$, are scaled by the value of vcScalarValueScaleFactorF.

Default: "$VMG$"

vcMinAnnoString1On
If this boolean resource is set False, VectorPlot will not display a string above or to the left (depending on the current value of vcMinAnnoOrientation) of the minimum annotation arrow. Otherwise, the string will be displayed.

Default: True

vcMinAnnoString2
Specifies the string to use above or to the left (depending on the current value of vcMinAnnoOrientation) of the arrow in the minimum vector annotation. The string may contain function codes and/or substitution substrings.

vcMagnitudeFormat determines the format of all numbers related to the vector field, and all numbers, except for the number generated from the substitution substring $MSF$, are scaled by the value of vcMagnitudeScaleFactorF. vcScalarValueFormat determines the format of all numbers related to the scalar field, and all numbers, except for the number generated from the substitution substring $SSF$, are scaled by the value of vcScalarValueScaleFactorF.

Default: "Minimum Vector"

vcMinAnnoString2On
If this boolean resource is set False, VectorPlot will not display a string below or to the right (depending on the current value of vcMinAnnoOrientation) of the minimum annotation arrow. Otherwise, the string will be displayed.

Default: True

vcMinAnnoTextDirection
This resource of type NhlTTextDirection specifies the direction of the text in the minimum vector annotation. There are two choices:
Down
Each character is placed below the previous character in the text string.
Across
Each character is placed to the right of the previous character in the text string.

Default: Across

vcMinAnnoZone
VectorPlot implements the vector minimum annotation as an embedded annotation. vcMinAnnoZone specifies the PlotManager zone assigned to the vector minimum annotation. The PlotManager Location Control Model requires this resource to allow control of the minimum annotation consistent with other annotations. If vcMinAnnoZone is set to 0, the positional origin is the center of the plot viewport; otherwise it is on or outside one of the sides of the viewport.

Default: 3

vcMinDistanceF
This resource specifies a minimum distance in NDC space that is to separate the data locations of neighboring vectors. Vectors are elimininated from the plot until there are no vectors closer than the specified distance. Note that if the realized length of a vector glyph is long enough, it is still possible that it may overlap neighboring glyphs. However, the grid point locations are guaranteed to be no closer than the distance specified. When this resource has its default value, 0.0, the thinning algorithm is not applied.

Default: 0.0

vcMinFracLengthF
If vcGlyphStyle is not set to WindBarb, this resource specifies, as a fraction of the reference length (vcRefLengthF), the length used to render the minimum magnitude vector. If vcMinMagnitudeF is greater than 0.0, its value is used as the minimum magnitude; otherwise the magnitude of the smallest vector appearing in the plot is used as the minimum magnitude. The lengths of the remaining vectors are determined by scaling proportionally between this length and the reference length. Setting vcMinFracLengthF to the value 1.0 causes all vectors to be drawn with the same length. If vcMinFracLengthF has its default value, 0.0, the vector length is strictly proportional to its magnitude.

If vcGlyphStyle is set to WindBarb, the value of vcMinFracLengthF is effectively forced to the value 1.0, and its set value is ignored.

Default: 0.0

vcMinLevelValF
When the vcLevelSelectionMode is ManualLevels, the value of vcMinLevelValF, if set, determines the lowest vector level. Otherwise, VectorPlot sets the vcMinLevelValF to a value equal to lowest vector level picked.

Default: <dynamic>

vcMinMagnitudeF
This resource specifies a minimum magnitude for elements of the vector field. Vectors with magnitudes less than this value will not be rendered in the vector field plot.

Default: 0.0

vcMonoFillArrowEdgeColor
When set True, the edge color for all filled vector arrows is set to a single HLU color index, as specified by the value of the scalar resource vcFillArrowEdgeColor. When False, the elements of the array resource vcLevelColors specify the edge color of each arrow based on the scalar quantity associated with the vector. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: True

vcMonoFillArrowFillColor
When set True, the fill color for all filled vector arrows is set to a single HLU color index, as specified by the value of the scalar resource vcFillArrowFillColor. When False, the elements of the array resource vcLevelColors specify the fill color of each arrow based on the scalar quantity associated with the vector. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: True

vcMonoLineArrowColor
When this resource is set True, line-drawn vector arrows are colored using a single HLU color index, as specified by the value of the scalar resource vcLineArrowColor. When False, the elements of the array resource vcLevelColors are used to set the color of each vector line individually based on the scalar quantity associated with the vector. This resource has an effect only when vcGlyphStyle is set to LineArrow or CurlyVector.

Default: True

vcMonoWindBarbColor
When this resource is set True, wind barb glyphs are colored using a single HLU color index, as specified by the value of the scalar resource vcWindBarbColor. When False, the elements of the array resource vcLevelColors are used to set the color of each wind barb glyph individually based on the scalar quantity associated with the vector. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: True

vcNoDataLabelOn
This boolean resource, when set True, causes a label to appear when a vectorplot is drawn without any data having been provided. Except for the label string, all attributes of this label, including its position, are set using resources belonging to the constant field label. When set False, no such label appears.

Default: True

vcNoDataLabelString
This resource contains the string that appears in the 'No Data' label if you draw a VectorPlot object without providing any data. No substitution substrings are allowed in this label, since all the substitutions depend on data being available. Except for the boolean switch that turns it on and off, all attributes of this label, including its position, are set using resources belonging to the constant field label.

Default: "NO VECTOR DATA"

vcPositionMode
This resource of type NhlTVectorPositionMode specifies how the vector arrow is positioned in the vector field plot relative to the actual data location. There are three possibilites:
ArrowHead
The head of the arrow is placed at the data location.
ArrowCenter
The center of the arrow is placed at the data location.
ArrowTail
The tail of the arrow is placed at the data location.

Default: ArrowCenter

vcRefAnnoAngleF
NOT YET IMPLEMENTED.

Default: 0.0

vcRefAnnoArrowAngleF
This resource specifies the angle, in degrees, of the arrow used in the reference vector annotation.

Default: 0.0

vcRefAnnoArrowEdgeColor
If vcRefAnnoArrowUseVecColor is set False, this resource specifies the HLU line color index used to render the arrow in the reference annotation. If vcRefAnnoArrowUseVecColor is set True, and either vcUseScalarArray or vcMonoLineArrowColor is True, the line color index is determined from the value of vcLineArrowColor. If vcRefAnnoArrowUseVecColor is set True otherwise, the line color index is determined based on the magnitude of the reference annotation vector and the vcLevelColors array resource.

Default: Foreground

vcRefAnnoArrowFillColor
If vcRefAnnoArrowUseVecColor is set False, this resource specifies the HLU fill color index used to render the arrow in the reference annotation. If vcRefAnnoArrowUseVecColor is set True, and either vcUseScalarArray or vcMonoFillArrowFillColor is True, the fill color index is determined from the value of vcFillArrowFillColor. If vcRefAnnoArrowUseVecColor is set True otherwise, the fill color index is determined based on the magnitude of the reference annotation vector and the vcLevelColors array resource. This resource has an effect only when vcGlyphStyle is set to FillArrow.

Default: Foreground

vcRefAnnoArrowLineColor
If vcRefAnnoArrowUseVecColor is set False, this resource specifies the HLU line color index used to render the arrow in the reference annotation. If vcRefAnnoArrowUseVecColor is set True, and either vcUseScalarArray or vcMonoLineArrowColor is True, the line color index is determined from the value of vcLineArrowColor. If vcRefAnnoArrowUseVecColor is set True otherwise, the line color index is determined based on the magnitude of the reference annotation vector and the vcLevelColors array resource.

Default: Foreground

vcRefAnnoArrowMinOffsetF
This resource specifies the minimum amount of space between the reference vector annotation arrow and the text on either side in units of the reference annotation font height.

Default: 0.25

vcRefAnnoArrowSpaceF
This resource specifies the minimum amount of space reserved for the reference vector annotation arrow in units of the reference annotation font height. More space may be used if the arrow extent (in units of the font height) plus twice the value of vcRefAnnoArrowMinOffsetF exceeds this value.

Default: 2.0

vcRefAnnoArrowUseVecColor
If this resource is set True, VectorPlot will base the coloring of the reference arrow on the colors used to draw the vector plot arrows as follows: if coloring by magnitude is in effect (vcUseScalarArray and and, depending on the value of vcGlyphStyle, the appropriate "mono" color flag is set False), then the color will be that assigned to vectors representing the magnitude of the reference annotation vector; otherwise, the color will be determined from the current values assigned to vcLineArrowColor and/or vcFillArrowFillColor. If vcRefAnnoArrowUseVecColor is False, then vcRefAnnoArrowLineColor and vcRefAnnoArrowFillColor control the color of the reference annotation arrow.

Default: True

vcRefAnnoBackgroundColor
This resource sets the background color used to fill the box surrounding the vector reference annotation. If you do not want the box to be filled at all, set vcRefAnnoBackgroundColor to Transparent (-1).

Default: Background

vcRefAnnoConstantSpacingF
Normally when vcRefAnnoFontQuality is set to High, VectorPlot draws the reference vector annotation text using proportional spacing. Setting the vcRefAnnoConstantSpacingF to a value greater than 0.0 overrides this behavior. Instead, the distance from the start of one character to the next is computed by multiplying a single standard character width by the value of vcRefAnnoConstantSpacingF. When vcRefAnnoConstantSpacingF has a value between 0.0 and 1.0, characters will overlap. A value of 1.0 implies, on average, no space between characters, while values increasing from 1.0 cause the space between characters to grow. This parameter is ignored when vcRefAnnoFontQuality is not High. Values less than 0.0 result in an error and are replaced with the default value.

Default: 0.0

vcRefAnnoExplicitMagnitudeF
By default, the arrow in the reference vector annotation is drawn at the size of the current VectorPlot reference magnitude. However, if you set this resource to a value greater than its default value of 0.0, the size of the arrow will reflect the vector magnitude represented by this value.

Default: 0.0

vcRefAnnoFont
This resource of type NhlTFont specifies the font used to render the vector reference annotation.

Default: "pwritx"

vcRefAnnoFontAspectF
This resource determines the shape of the reference vector annotation characters. Values increasing from 1.0 result in characters that appear thinner. Values decreasing from 1.0 make the characters appear wider. Values less than or equal to 0.0 result in a WARNING message and a restoration of the default value.

Default: 1.3125

vcRefAnnoFontColor
This resource specifies the HLU color index used to render vector reference annotation text.

Default: Foreground

vcRefAnnoFontHeightF
This resource controls the height, in NDC units, of characters used in the text of the reference vector annotation. The character width scales proportionally, unless you also modify the aspect ratio using the vcRefAnnoFontAspectF resource. The reference annotation font height scales with changes to the viewport width, unless you explicitly set vcRefAnnoFontHeightF during the same call.

Default: <dynamic>

vcRefAnnoFontQuality
This resource of type NhlTFontQuality determines the quality of the font used to draw the VectorPlot vector reference annotation.

Default: High

vcRefAnnoFontThicknessF
Sets the thickness of the line used to draw vector reference annotation text. The value acts as a multiplier of a (device-dependent) unit thickness. This resource is ignored when the vcRefAnnoFont specifies a filled font (font indexes 21-22, 25-26, 29-30, and 33-37).

Default: 1.0

vcRefAnnoFuncCode
This resource of type NhlTCharacter sets the function code character for the reference annotation strings.

Note: the default function code was a colon (:) in NCL Versions 6.0.0 and earlier.

Default: ~

vcRefAnnoJust
This resource of type NhlTJustification, after constraint to an appropriate value based on vcRefAnnoSide, sets the justification of the vector reference annotation with respect to its base location. The PlotManager Location Control Model requires this resource to allow control of the vector reference annotation consistent with other annotations.

Default: TopRight

vcRefAnnoOn
If this boolean resource is set False, VectorPlot will not draw the reference vector annotation.

Default: True

vcRefAnnoOrientation
NOT YET IMPLEMENTED

This resource of type NhlTOrientation specifies whether the elements of the reference vector annotation (two strings with an arrow representing a vector magnitude in between) are stacked vertically or placed side by side horizontally.

Default: Vertical

vcRefAnnoOrthogonalPosF
vcRefAnnoOrthogonalPosF sets the coordinate of the base location of the vector reference annotation orthogonal to the current vcRefAnnoSide and directed away from the center of the viewport. The PlotManager Location Control Model requires this resource to allow control of the vector reference annotation consistent with other annotations.

Default: 0.02

vcRefAnnoParallelPosF
vcRefAnnoParallelPosF specifies the coordinate of the base location of the vector reference annotation parallel to the current vcRefAnnoSide and directed toward increasing NDC values. The PlotManager Location Control Model requires this resource to allow control of the vector reference annotation consistent with other annotations.

Default: 1.0

vcRefAnnoPerimColor
This resource sets the HLU color index used to draw the perimeter of the vector reference annotation.

Default: Foreground

vcRefAnnoPerimOn
vcRefAnnoPerimOn is a boolean resource that determines whether VectorPlot will draw an outline around the perimeter of the box surrounding the reference vector annotation. If set False, no outline will be drawn.

Default: True

vcRefAnnoPerimSpaceF
vcRefAnnoPerimSpaceF determines the spacing or margin between the text of the reference vector annotation and its edge as a fraction of current reference annotation font height.

Default: 0.33

vcRefAnnoPerimThicknessF
This resource determines the thickness of the perimeter line around the vector reference annotation. The value acts as a multiplier of a (device-dependent) unit thickness.

Default: 1.0

vcRefAnnoSide
This resource of type NhlTPosition determines where to place the vector reference annotation in relation to the sides of the plot object. The PlotManager Location Control Model requires this resource to allow control of the vector reference annotation consistent with other annotations. Its value determines a coordinate system origin and the direction of the positional resources vcRefAnnoParallelPosF and vcRefAnnoOrthogonalPosF. It also constrains the value of vcRefAnnoJust appropriately. There are four settings, which behave as follows, unless vcRefAnnoZone is set to one of the special zones (0 or 1):
Top
The PlotManager locates the vector reference annotation relative to a line paralleling the top viewport boundary. vcRefAnnoOrthogonalPosF increases in the direction of increasing NDC Y-Axis values and is constrained to positive values. vcRefAnnoParallelPosF increases in the direction of increasing NDC X-Axis values. vcRefAnnoJust is constrained to BottomRight, BottomCenter, or BottomLeft.
Bottom
The PlotManager locates the vector reference annotation relative to a line paralleling the bottom viewport boundary. vcRefAnnoOrthogonalPosF increases in the direction of decreasing NDC Y-Axis values and is constrained to positive values. vcRefAnnoParallelPosF increases in the direction of increasing NDC X-Axis values. vcRefAnnoJust is constrained to TopRight, TopCenter, or TopLeft.
Right
The PlotManager locates the vector reference annotation relative to a line paralleling the right viewport boundary. vcRefAnnoOrthogonalPosF increases in the direction of increasing NDC X-Axis values and is constrained to positive values. vcRefAnnoParallelPosF increases in the direction of increasing NDC Y-Axis values. vcRefAnnoJust is constrained to TopLeft, CenterLeft, or BottomLeft.
Left
The PlotManager locates the vector reference annotation relative to a line paralleling the left viewport boundary. vcRefAnnoOrthogonalPosF increases in the direction of decreasing NDC X-Axis values and is constrained to positive values. vcRefAnnoParallelPosF increases in the direction of increasing NDC Y-Axis values. vcRefAnnoJust is constrained to TopRight, CenterRight, or BottomRight.
If vcRefAnnoZone is set to 0, the PlotManager locates the vector reference annotation relative to the viewport center. If vcRefAnnoZone is 1, the direction of the vcRefAnnoOrthogonalPosF is opposite to the specification given above. Also if the vcRefAnnoZone is either 0 or 1, vcRefAnnoJust is not constrained, and vcRefAnnoOrthogonalPosF may take on negative values.

Default: Bottom

vcRefAnnoString1
Specifies the string to use above or to the left (depending on the current value of vcRefAnnoOrientation) of the arrow in the reference vector annotation. The string may contain function codes and/or substitution substrings.

vcMagnitudeFormat determines the format of all numbers related to the vector field, and all numbers, except for the number generated from the substitution substring $MSF$, are scaled by the value of vcMagnitudeScaleFactorF. vcScalarValueFormat determines the format of all numbers related to the scalar field, and all numbers, except for the number generated from the substitution substring $SSF$, are scaled by the value of vcScalarValueScaleFactorF.

Default: "$VMG$"

vcRefAnnoString1On
If this boolean resource is set False, VectorPlot will not display a string above or to the left (depending on the current value of vcRefAnnoOrientation) of the reference annotation arrow. Otherwise, the string will be displayed.

Default: True (False for some of the gsn_csm_vector_xxx plotting functions)

vcRefAnnoString2
Specifies the string to use above or to the left (depending on the current value of vcRefAnnoOrientation) of the arrow in the reference vector annotation. The string may contain function codes and/or substitution substrings.

vcMagnitudeFormat determines the format of all numbers related to the vector field, and all numbers, except for the number generated from the substitution substring $MSF$, are scaled by the value of vcMagnitudeScaleFactorF. vcScalarValueFormat determines the format of all numbers related to the scalar field, and all numbers, except for the number generated from the substitution substring $SSF$, are scaled by the value of vcScalarValueScaleFactorF.

Default: "Reference Vector"

vcRefAnnoString2On
If this boolean resource is set False, VectorPlot will not display a string below or to the right (depending on the current value of vcRefAnnoOrientation) of the reference annotation arrow. Otherwise, the string will be displayed.

Default: True

vcRefAnnoTextDirection
This resource of type NhlTTextDirection specifies the direction of the text in the reference vector annotation. There are two choices:
Down
Each character is placed below the previous character in the text string.
Across
Each character is placed to the right of the previous character in the text string.

Default: Across

vcRefAnnoZone
VectorPlot implements the vector reference annotation as an embedded annotation. vcRefAnnoZone specifies the PlotManager zone assigned to the vector reference annotation. The PlotManager Location Control Model requires this resource to allow control of the reference annotation consistent with other annotations. If vcRefAnnoZone is set to 0, the positional origin is the center of the plot viewport; otherwise it is on or outside one of the sides of the viewport.

Default: 3

vcRefLengthF
If vcGlyphStyle is set to LineArrow or FillArrow, this resource specifies, in units of NDC, the length used to render vectors with a magnitude equal to the reference magnitude, as specified by vcRefMagnitudeF. If vcGlyphStyle is set to WindBarb, it specifies the length of the wind barb shaft plus the projected length of a full tick along the shaft axis. If vcGlyphStyle is set to CurlyVector it specifies the path length of the curve used to render render vectors with a magnitude equal to the reference magnitude. The path length is calculated as the sum of the individual steps used to generate the curve. If vcRefLengthF is not specified, its value is dynamically calculated based on the number of elements in the vector field and the size of the VectorPlot viewport.

Default: <dynamic>

vcRefMagnitudeF
This resource specifies the magnitude used as the reference magnitude used for the vector field plot. Vectors equal in magnitude to the reference magnitude will be rendered at the length specified by the resource vcRefLengthF. If vcRefMagnitudeF has its default value, 0.0, the maximum magnitude in the vector field will be used as the reference magnitude.

Default: 0.0

vcScalarFieldData
Specifies the id of a ScalarField data object. If this resource is set with a valid ScalarField object and the resource vcUseScalarArray is set True, VectorPlot will use the scalar array data for coloring the arrows used to render the vector field plot. In order for VectorPlot to consider the ScalarField object valid, it must find that it has the same number of elements along each dimension as are found in the VectorField object.

Note that currently the number of elements is checked only after strides and subsetting are applied. The data coordinate extents set for the ScalarField object are ignored. For now, the data coordinate extents of the processed ScalarField data are assumed to coincide with the data coordinate extents of the VectorField data.

Default: none

vcScalarMissingValColor
When vcUseScalarArray is True, this resource sets the HLU index of the fill or line color used to draw vectors whose associated scalar value is missing. If vcScalarMissingValColor has the value Transparent (-1), the vector will not be drawn at all.

Default: Foreground

vcScalarValueFormat
The vcScalarValueFormat resource is a string that specifies the printing format for vector field values according to the HLU Floating Point Format Specification scheme. This resource controls the formatting of any number representing VectorField data when used in a VectorPlot annotation.

Default: "*+^sg"

vcScalarValueScaleFactorF
vcScalarValueScaleFactorF is a read-only resource that contains the current scale factor that applies to annotations with numbers representing values from the associated ScalarField object. Multiplying the numbers in the annotations by the value of vcScalarValueScaleFactorF gives the actual scalar values the numbers represent. VectorPlot calculates its value based on the maximum absolute value in the scalar field data, the current mode of the enumerated resource, vcScalarValueScalingMode, and perhaps the value of vcScalarValueScaleValueF. Its value may also be influenced by the number of significant digits specified by the format specification resource, vcScalarValueFormat.

Default: 1.0

vcScalarValueScaleValueF
The interpretation of vcScalarValueScaleValueF depends on the value of the enumerated resource vcScalarValueScalingMode. When vcScalarValueScalingMode is set to ScaleFactor, values are divided by the value of vcScalarValueScaleValueF to obtain the numbers appearing in VectorPlot object labels. If vcScalarValueScalingMode is set to ConfineToRange, the vcScalarValueScaleValueF represents an exclusive upper bound for the numbers used to represent the data values. For other values of vcScalarValueScalingMode, the vcScalarValueScaleValueF resource is ignored.

Default: 1.0

vcScalarValueScalingMode
This resource of type NhlTScalingMode determines how to scale numbers related to the scalar field data used to color the vectors when these numbers appear in the annotations provided by VectorPlot. There are five choices:
ScaleFactor
The VectorPlot object divides the scalar value by the value of vcScalarValueScaleValueF to obtain the number that appears in the label.
ConfineToRange
The VectorPlot object uses vcScalarValueScaleValueF as an exclusive upper bound. A scale factor is selected such that the scaled value representing the scalar maximum absolute value will be less than vcScalarValueScaleValueF, but greater than or equal to vcScalarValueScaleValueF divided by 10.0. As an example, setting vcScalarValueScaleValueF to 100.0 would result in the number used to represent the maximum absolute value falling in the range 10.0 to 99.999....
TrimZeros
The VectorPlot object selects a scale factor such that the number representing the value with the maximum absolute value will have the fewest possible extra zeros. If the maximum absolute value were 245000, for instance, it would scale to 245. If it were 0.000245, it would scale to 0.245. (The zero conventionally placed before the decimal point of a number less than 1.0 is not considered.)
MaxSigDigitsLeft
The VectorPlot object selects a scale factor such that the number representing the value with the maximum absolute value will have its rightmost significant digit directly to the left of the decimal point. The number of significant digits is determined by the format string resource, vcScalarValueFormat.
AllIntegers
The VectorPlot object selects a scale factor such that the numbers representing vector levels (as determined by examination of the values of the vcLevels array) are reduced to integers.
In each case, the scale factor selected is placed into the read-only resource, vcScalarValueScaleFactorF.

Default: ScaleFactor

vcSpanLevelPalette
Available in version 6.1.0 and later.

If set to True, and if vcLevelColors is not set using explicit values, then VectorPlot automatically spans the vcLevelPalette resource to determine color index values for vcLevelColors. If vcLevelPalette is not set then the wkColorMap resource is spanned instead. If set to False, then VectorPlot uses consecutively ascending values to populate vcLevelColors.

If the colors are derived from vcLevelPalette the first color will be determined from element 0, whereas if they are derived from wkColorMap, the first color will come from element 2. This is because wkColorMap contains special elements (0 and 1) for the Background and Foreground colors, whereas the palette-type resources do not.

Default: True

vcUseRefAnnoRes
If this boolean resource is True, the values for many resources belonging to the reference vector annotation are copied to the minimum vector annotation and the zero field annotation, allowing you to ensure consistency in the appearance of each of these annotations without the need to set each resource individually. The following text attribute resource values are copied to the corresponding resources of both the minimum vector annotation and the zero field annotation: The following resources are copied only to the corresponding minimum vector annotation resource: Note that the zonal location resources, angle, the string contents, the "on" switches, and the explicit magnitude resources are not copied.

Default: False

vcUseScalarArray
If this boolean resource is set True, the resource vcScalarFieldData is set with a valid ScalarField object, and the appropriate VectorPlot resources are set to enable multi-colored vector glyphs, then the ScalarField data are used to select the level (and hence the color index) assigned to each glyph. Otherwise, when multi-colored vector glyphs are enabled, vector coloring will be based on the magnitude of the vectors.

Default: False

vcVectorDrawOrder
This resource of type NhlTDrawOrder determines when the vector arrows are drawn relative to the drawing of other elements of a composite plot. There are three choices:
PreDraw
Draw vector arrows before the standard draw phase; the arrows will be overlaid by any subsequently drawn elements.
Draw
Draw vector arrows during the standard draw phase; the arrows will overlay any elements drawn during the predraw phase, but will underlie elements drawn during the postdraw phase.
PostDraw
Draw vector arrows after the standard draw; the arrows will overlay any elements drawn during the predraw and draw phases.

Default: Draw

vcVectorFieldData
Specifies the id of a VectorField data object. There is no default for this resource; it is the only resource that must be set in order for the VectorPlot object to draw a plot. You may create a VectorPlot object without setting the vcVectorFieldData, and auxiliary annotations such as tick marks and titles may appear as the result of a draw, but the VectorPlot itself will not show up. The VectorField object can provide either regularly spaced or irregular rectangular gridded data to the VectorPlot object, and it provides a number of resources for controlling the ingestion of the raw data.

Default: none

vcWindBarbCalmCircleSizeF
This resource sets the diameter of the circle used to represent small vector magnitudes as a fraction of the overall wind barb length. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: 0.25

vcWindBarbColor
When vcMonoWindBarbColor is set True, this resource sets a uniform color index for all polygon and polyline elements used to draw wind barb glyphs. If set to Transparent (-1), the line color index will be constrained to the value Foreground (1). This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: Foreground

vcWindBarbLineThicknessF
This resource sets the thickness of the polyline elements used to draw wind barb glyphs. The value acts as a multiplier of a (device-dependent) unit thickness. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: 1.0

vcWindBarbScaleFactorF
This resource sets the factor by which the vector magnitudes as calculated by the wind barb drawing routines are to be scaled. It can be used to convert vector data given in other units into the conventional units used with wind barbs, which is knots. Note that this scale factor resource is entirely independent of the vcMagnitudeScaleFactorF and vcMagnitudeScaleValueF resources which influence numerical strings in annotations associated with VectorPlot. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: 1.0

vcWindBarbTickAngleF
This resource set the angle of the wind barb ticks measured clockwise from the vector direction. It also sets the angle between the hypotenuse of the triangle defining the pennant polygon and the vector direction. You can render southern hemisphere wind barbs, which by convention have their ticks and pennants on the other side of the shaft, by setting vcWindBarbTickAngleF to a negative value. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: 62.0

vcWindBarbTickLengthF
This resource sets the length of a wind barb tick as a fraction of the overall length of a wind barb. The wind barb length is defined as the length of the wind barb shaft plus the projection of a full wind barb tick along the axis of the shaft. Therefore, increasing this value, for a given vector reference length, has the effect of reducing the length of the shaft itself somewhat. You may need to increase vcRefLengthF to compensate. This resource also sets the hypotenuse length of the triangle defining the pennant polygon. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: 0.3

vcWindBarbTickSpacingF
This resource sets the spacing of the wind barb ticks along the wind barb shaft as a fraction of the overall wind barb length. Half this distance is used as the spacing between adjacent wind barb pennants. Note that VectorPlot does nothing to prevent ticks or pennants from continuing off the end of the shaft if high magnitude flow fields are rendered. This resource has an effect only when vcGlyphStyle is set to WindBarb.

Default: 0.125

vcZeroFLabelAngleF
This resource specifies the angle, in degrees, of the zero field label text and its surrounding box.

Default: 0.0

vcZeroFLabelBackgroundColor
This resource sets the background color used to fill the box surrounding the zero field label. If you do not want the box to be filled at all, set vcZeroFLabelBackgroundColor to Transparent (-1).

Default: Background

vcZeroFLabelConstantSpacingF
Normally when vcZeroFLabelFontQuality is set to High, the VectorPlot object writes zero field label text with proportional spacing. Setting the vcZeroFLabelConstantSpacingF to a value greater than 0.0 overrides this behavior. Instead, the distance from the start of one character to the next is computed by multiplying a single standard character width by the value of vcZeroFLabelConstantSpacingF. When vcZeroFLabelConstantSpacingF has a value between 0.0 and 1.0, characters will overlap. A value of 1.0 implies, on average, no space between characters, while values increasing from 1.0 cause the space between characters to grow. This parameter is ignored when vcZeroFLabelFontQuality is not High. Values less than 0.0 result in an error and are replaced with the default value.

Default: 0.0

vcZeroFLabelFont
This resource of type NhlTFont specifies the font used to render the zero field label.

Default: 0

vcZeroFLabelFontAspectF
This resource determines the shape of the zero field label characters. Values increasing from 1.0 result in characters that appear thinner. Values decreasing from 1.0 make the characters appear wider. Values less than or equal to 0.0 result in a WARNING message and a restoration of the default value.

Default: 1.3125

vcZeroFLabelFontColor
This resource specifies the HLU color index used to render zero field label text.

Default: True

vcZeroFLabelFontHeightF
This resource controls the height, in NDC units, of characters used in the text of the zero field label. The character width scales proportionally, unless you also modify the aspect ratio using the vcZeroFLabelFontAspectF resource. The zero label text height scales with changes to the viewport width, unless you explicitly set vcZeroFLabelFontHeightF during the same call.

Default: <dynamic>

vcZeroFLabelFontQuality
This resource of type NhlTFontQuality determines the quality of the font used to draw the VectorPlot zero field label.

Default: High

vcZeroFLabelFontThicknessF
Sets the thickness of the line used to draw zero field label text. The value acts as a multiplier of a (device-dependent) unit thickness. This resource is ignored when the vcZeroFLabelFont specifies a filled font (font indexes 21-22, 25-26, 29-30, and 33-37).

Default: 1.0

vcZeroFLabelFuncCode
This resource of type NhlTCharacter sets the function code character that the low level utilities will use when parsing the zero field label string.

Note: the default function code was a colon (:) in NCL Versions 6.0.0 and earlier.

Default: ~

vcZeroFLabelJust
This resource of type NhlTJustification, after constraint to an appropriate value based on vcZeroFLabelSide, sets the justification of the zero field label annotation with respect to its base location. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations.

Default: CenterCenter

vcZeroFLabelOn
The VectorPlot object draws a zero field label annotation only when vcZeroFLabelOn is set True and the ScalarField data are determined to consist entirely of zero magnitude vectors within the limits of the available precision.

Default: True

vcZeroFLabelOrthogonalPosF
vcZeroFLabelOrthogonalPosF sets the coordinate of the base location of the zero field label annotation orthogonal to the current vcZeroFLabelSide and directed away from the center of the viewport. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations.

Default: 0.0

vcZeroFLabelParallelPosF
vcZeroFLabelParallelPosF specifies the coordinate of the base location of the zero field label annotation parallel to the current vcZeroFLabelSide and directed toward increasing NDC values. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations.

Default: 0.0

vcZeroFLabelPerimColor
This resource sets the HLU color index used to draw the perimeter of the zero field label box.

Default: Foreground

vcZeroFLabelPerimOn
vcZeroFLabelPerimOn is a boolean resource that determines whether VectorPlot will draw an outline around the perimeter of the box surrounding vector zero field label. If set False, no outline will be drawn.

Default: True

vcZeroFLabelPerimSpaceF
vcZeroFLabelPerimSpaceF determines the spacing, or margin, between the text of the zero field label and the edge of the zero field label box as a fraction of the current label text height.

Default: 0.33

vcZeroFLabelPerimThicknessF
This resource determines the thickness of the perimeter line around the zero field label box. The value acts as a multiplier of a (device-dependent) unit thickness.

Default: 1.0

vcZeroFLabelSide
This resource of type NhlTPosition determines where to place the zero field annotation in relation to the sides of the plot object. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations. Its value determines a coordinate system origin and the direction of the positional resources vcZeroFLabelParallelPosF and vcZeroFLabelOrthogonalPosF. It also constrains the value of the vcZeroFLabelJust appropriately. There are four settings, which behave as follows, unless vcZeroFLabelZone is set to one of the special zones (0 or 1):
Top
The PlotManager locates the zero field label annotation relative to a line paralleling the top viewport boundary. vcZeroFLabelOrthogonalPosF increases in the direction of increasing NDC Y-Axis values and is constrained to positive values. vcZeroFLabelParallelPosF increases in the direction of increasing NDC X-Axis values. vcZeroFLabelJust is constrained to BottomRight, BottomCenter, or BottomLeft.
Bottom
The PlotManager locates the zero field label annotation relative to a line paralleling the bottom viewport boundary. vcZeroFLabelOrthogonalPosF increases in the direction of decreasing NDC Y-Axis values and is constrained to positive values. vcZeroFLabelParallelPosF increases in the direction of increasing NDC X-Axis values. vcZeroFLabelJust is constrained to TopRight, TopCenter, or TopLeft.
Right
The PlotManager locates the zero field label annotation relative to a line paralleling the right viewport boundary. vcZeroFLabelOrthogonalPosF increases in the direction of increasing NDC X-Axis values and is constrained to positive values. vcZeroFLabelParallelPosF increases in the direction of increasing NDC Y-Axis values. vcZeroFLabelJust is constrained to TopLeft, CenterLeft, or BottomLeft.
Left
The PlotManager locates the zero field label annotation relative to a line paralleling the left viewport boundary. vcZeroFLabelOrthogonalPosF increases in the direction of decreasing NDC X-Axis values and is constrained to positive values. vcZeroFLabelParallelPosF increases in the direction of increasing NDC Y-Axis values. vcZeroFLabelJust is constrained to TopRight, CenterRight, or BottomRight.
If vcZeroFLabelZone is set to 0, The PlotManager locates the zero field label annotation relative to the viewport center. If vcZeroFLabelZone is 1, the direction of the vcZeroFLabelOrthogonalPosF is opposite to the specification given above. Also if the vcZeroFLabelZone is either 0 or 1, vcZeroFLabelJust is not constrained, and vcZeroFLabelOrthogonalPosF may take on negative values.

Default: Bottom

vcZeroFLabelString
Specifies the string to use when drawing a zero field label. The string may contain function codes.

Default: "ZERO FIELD"

vcZeroFLabelTextDirection
This resource of type NhlTTextDirection specifies the direction of the text in the zero field label. There are two choices:
Down
Each character is placed below the previous character in the text string.
Across
Each character is placed to the right of the previous character in the text string.
These descriptions apply before rotation due to vcZeroFLabelAngleF.

Default: Across

vcZeroFLabelZone
VectorPlot implements the zero field label as an embedded annotation. vcZeroFLabelZone specifies the PlotManager zone assigned to the zero field annotation. The PlotManager Location Control Model requires this resource to allow control of the zero field label consistent with other annotations. If vcZeroFLabelZone is set to 0, the positional origin is the center of the plot viewport; otherwise it is on or outside one of the sides of the viewport.

If you create a VectorPlot object without an active PlotManager, by setting tfPlotManagerOn False, then VectorPlot manages the zero field annotation by itself. In this case, the vcZeroFLabelZone resource is not as meaningful.

Default: 0