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getFillValue

Retrieves the _FillValue of a variable, if present.

Prototype

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

	function getFillValue (
		x  : numeric   
	)

Arguments

A numeric array of any dimensionality.

Return value

A scalar value equal to the _FillValue of x. Same type as x

Description

Determines the _FillValue by first looking to see if the variable has a missing value attribute. This can be an attribute named "_FillValue" or "missing_value". As of version 4.3.0, if it has neither, then a _FillValue of "No_FillValue" is returned.

Important behavior change

Prior to version 4.3.0, getFillValue would return the default _FillValue if a variable did not have _FillValue associated with it.

For example, in the line below:

  q = new( 10, typeof(w), getFillValue(w))

if "w" is of type "float" and if "w" did not have a _FillValue, then getFillValue would return the _FillValue for a variable of type "float". Hence, q@_FillValue = -999. In some cases this result was not desired.

In 4.2.0.a034, the string "No_FillValue" was introduced for use within the new statement. Use of "No_FillValue" as the third argument of new would result in no _FillValue being assigned to "q".

A side effect of this new behavior is that the following will result in a fatal error:

  q@_FillValue = getFillValue(w)

if the variable has no _FillValue associated with it. The reason is the the string "No_FillValue" can not be assigned to "q" unless q is of type string.

It should be noted that getFillValue was only intended to be used within the new statement.

Examples

Example 1: Create a new variable and assign the _FillValue associated with some variable (here, "w"). If "w" has no _FillValue, then "q" will have no _FillValue.