dim_stddev

For each index of dimensions 0..n-2, this function computes the standard deviation of the n-1 dimension.

Synopsis

	function dim_stddev(
		x : numeric
	)

Arguments

x
An array of one or more numeric values of any dimensionality

Description

The dim_stddev function computes the standard deviation of all elements of the n-1 dimension for each index of the dimensions 0..n-2. dim_stddev ignores missing values (x@_FillValue). The output dimensionality is the same as the first n-2 dimensions of the input. To determine the number of data points used to calculate the standard deviation use: 
   N = num(.not.ismissing(x))
Technically, this function calculates the population standard deviation.

Example

The following is a simplistic example that demonstrates how dim_stddev works. Try running this example and print out the values to get a better idea of how dim_stddev works. 
begin
;
;       Create example array
;
        a = onedtond(ispan(1,150,1),(/3,5,10/))
;
;       Assign dimension names
;
        a!0 = "time"
        a!1 = "latitude"
        a!2 = "longitude"
;
;       Compute standard deviation of dimension "longitude" at all time and latitude points
;
        pxy = dim_stddev(a)
        N = num(.not.ismissing(a))   ; compute number of values used in calculation
;
;       Compute standard deviation of dimension "time" at all points latitude and longitude points
;       The following uses Named Subscripting to reorder the input array
;       such that time is the n-1 dimension.
;
        pyz = dim_stddev( a(latitude | :, longitude | : , time | :) )

end

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$Revision: 1.7 $ $Date: 1999/03/15 16:59:47 $