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NhlDataPolyline

Draws a polyline using data coordinates.

Prototype

	procedure NhlDataPolyline (
		objects [*] : graphic,  
		style   [*] : graphic,  
		x       [*] : float,    
		y       [*] : float     
	)

Arguments

objects

An array of plot objects. Plot objects are created by using one of the many GSN plotting functions, or by calling the NCL create language construct.

style

A scalar or an array of the same length as objects containing NCL style objects.

x
y

Arrays containing the X and Y coordinates of the polyline in data coordinates. They must be the same length.

Description

NhlDataPolyline draws the polyline defined by the pair of vectors x and y using either a single style object or the corresponding style object from the style parameter. The vectors x and y contain values in data coordinates. The coordinates are mapped using the NCL object's data transformation and drawn as a polyline clipped to the viewports of each NCL plot object in the objects array.

The difference between the NCL version and the HLU version is that the NCL version draws the polyline over one or more HLU plot objects using one or more styles, and the NCL version does not need the length of the x and y parameters because this information is inherent in NCL data. In the HLU version, NULL can be used to use the default graphic style object. In NCL, however, the default style object must be retrieved from the workstation parent using the wkDefGraphicStyleId resource and the getvalues statement.

For more information on controlling how the polyline is drawn, see the GraphicStyle class description.

Note: it is recommended that you use the gsn_polyline procedure instead, because it allows you to input X and Y arrays of any numeric type, it checks for missing values, it doesn't require a style object, and it allows you to include a list of optional resources.

See Also

gsn_polygon, gsn_polygon_ndc, gsn_polyline, gsn_polyline_ndc, gsn_polymarker, gsn_polymarker_ndc, NhlDataPolygon, NhlDataPolymarker, NhlNDCPolygon, NhlNDCPolymarker, NhlNDCPolyline

Examples

Example 1

This example creates an XY object and then draws a polygon, polymarkers, and a polyline on it. See example 2 for the same thing accomplished with GSN functions.

begin
;
; Create workstation.
;
  wks = create "poly" xWorkstationClass defaultapp end create

;
; Get the default GraphicStyle id and change some resource values.
;
  getvalues wks
    "wkDefGraphicStyleId" : gsid
  end getvalues

  setvalues gsid
    "gsLineColor"      : "orange"
    "gsLineThicknessF" : 2.0
    "gsFillColor"      : "Navy"
    "gsMarkerIndex"    : 12
    "gsMarkerSizeF"    : 0.02
    "gsMarkerColor"    : "yellow"
  end setvalues

;
; Create a data object.
;
  npts = 500
  x    = fspan(0,npts-1,npts)
  y    = 500.+ 0.9 * x * sin(0.031415926535898*x)

  dataid = create "data" coordArraysClass noparent
    "caYArray" : y
  end create

  xy = create "xy" xyPlotClass wks
    "xyCoordData" : dataid
  end create

  draw(xy)

;
; Draw some primitives.
;
  plx = x
  ply = 500. + 0.5 * x * sin(0.031415926535898*x)
  NhlDataPolyline(xy,gsid,plx,ply)

  pgx = (/ 100., 200., 200., 100., 100. /)
  pgy = (/ 200., 200., 300., 300., 200. /)
  NhlDataPolygon(xy,gsid,pgx,pgy)

  pmx = (/ 200., 150., 200., 250. /)
  pmy = (/ 900., 800., 700., 800. /)
  NhlDataPolymarker(xy,gsid,pmx,pmy)

  frame(wks)
end
Example 2

This example is identical to example 1, except it shows how to use GSN functions to accomplish the same thing with slightly less code:

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"

begin
  wks = gsn_open_wks("x11","test")

;
; Create some dummy data.
;
  npts = 500
  x    = fspan(0,npts-1,npts)
  y    = 500.+ 0.9 * x * sin(0.031415926535898*x)

;
; Set up some XY plot resources.
;
  xyres          = True
  xyres@gsnFrame = False
;
; Create and draw the XY plot.
;
  xy = gsn_y(wks,y,xyres)

;
; Set up some primitive resources.
;
  gsres                  = True
  gsres@gsLineColor      = "orange"
  gsres@gsLineThicknessF = 2.0
  gsres@gsFillColor      = "Navy"
  gsres@gsMarkerIndex    = 12
  gsres@gsMarkerSizeF    = 0.02
  gsres@gsMarkerColor    = "yellow"

;
; Draw some primitives.
;
  plx = x
  ply = 500. + 0.5 * x * sin(0.031415926535898*x)
  gsn_polyline(wks,xy,plx,ply,gsres)

  pgx = (/ 100., 200., 200., 100., 100. /)
  pgy = (/ 200., 200., 300., 300., 200. /)
  gsn_polygon(wks,xy,pgx,pgy,gsres)

  pmx = (/ 200., 150., 200., 250. /)
  pmy = (/ 900., 800., 700., 800. /)
  gsn_polymarker(wks,xy,pmx,pmy,gsres)

  frame(wks)
end