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getFillValue

Retrieves the _FillValue of a variable, if present, for use in a new statement.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"  ; This library is automatically loaded
                                                             ; from NCL V6.2.0 onward.
                                                             ; No need for user to explicitly load.

	function getFillValue (
		x  : numeric   
	)

Arguments

x

A numeric array of any dimensionality.

Description

This function is only intended to be used within the new statement. It returns three possible values:

  • x@_FillValue, if x@_FillValue is present

  • x@missing_value, if x@_FillValue is not present and x@missing_value is

  • "No_FillValue" if neither x@_FillValue or x@missing_value are present

The string "No_FillValue" has a special meaning for the new statement, and that is that no _FillValue attribute should be set.

Note: this function cannot not be used in the following manner:

  q@_FillValue = getFillValue(w)

because if the variable "w" has no _FillValue associated with it, then you will be effectively trying to set q@_FillValue = "No_FillValue", which will cause a fatal error if "q" is a numeric variable.

Important backwards-incompatibility change

Prior to version 4.3.0, if a variable did not have a _FillValue or missing_value attribute set, then this function would return the default _FillValue for the given type instead of "No_FillValue". In some cases this result was not desired, so this function was updated in NCL V4.3.0 to instead return the string "No_FillValue".

See Also

There are many metadata tools for dealing with missing values.

Examples

Example 1

Assume xf is a float array with a _FillValue of 1e20. The following code:

     q = new( 10, float, getFillValue(xf))  
     printVarSummary(q)

will produce the following output:

Variable: q
Type: float
Total Size: 40 bytes
            10 values
Number of Dimensions: 1
Dimensions and sizes:[10]
Coordinates: 
Number Of Attributes: 1
_FillValue :1e+20

Example 2

Assume xd is a double array with a missing_value of 9.969209968386869e+36. The following code:

     qd = new( (/10,20/), double, getFillValue(xd))  
     printVarSummary(qd)
will produce the following output:

Variable: qd
Type: double
Total Size: 1600 bytes
            200 values
Number of Dimensions: 2
Dimensions and sizes:[10] x [20]
Coordinates: 
Number Of Attributes: 1
_FillValue :9.969209968386869e+36

Example 3

Assume xi is an integer array with no metadata whatsoever. The following code:

     qi = new( (/10,20/), integer, getFillValue(xi))  
     printVarSummary(qi)
will produce the following output:

Variable: qi
Type: integer
Total Size: 800 bytes
            200 values
Number of Dimensions: 2
Dimensions and sizes:[10] x [20]
Coordinates: