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stat4

Calculates estimates of the first four moments (mean, variance, skewness, and kurtosis) of the given input.

Prototype

	procedure stat4 (
		x        : numeric,  
		xmean    : float,    ; or double
		xvar     : float,    ; or double
		xskew    : float,    ; or double
		xkurt    : float,    ; or double
		nptused  : integer   
	)

Arguments

x

An array of any dimensionality. Missing values should be indicated by x@_FillValue. If x@_FillValue is not set, then the NCL default missing value will be assumed.

xmean
xvar
xskew
xkurt

(output)
Variables that will contain the mean, sample variance, coefficient of skewness, and kurtosis of x. The dimensions should be the same as x, with the rightmost dimension omitted (or a scalar if x is one-dimensional). Space for these variables must be explicitly allocated by the user.

nptused

(output)
Variable that will contain the number of points used. It must have the same dimensionality as xmean, and space for it must be explicitly allocated by the user.

Description

stat4 calculates estimates of the first four moments (mean, variance, skewness, and kurtosis) of the rightmost dimension of x containing missing data.

If ndims represents the number of dimensions in x, then for the leftmost dimensions 0 to ndims-2, the calculations are done on the rightmost dimension (ndims-1th dimension) of the input array.

This function will be updated in V5.0.0 so that if a subarray of x contains all missing values, stat4 will return missing values in the appropriate locations rather than quitting with a fatal error.

See Also

stat2, stat_medrng, stat_trim

Examples

Run the following example, and then print out the various variables to see how stat2, stat4, stat_medrng, and stat_trim work:

begin
;
; Define a 3 x 2 x 2 array
;
   x = (/(/(/1.,2./),(/3.,4./)/),(/(/5.,6./),(/-999,8./)/),\
         (/(/9.,10./),(/11.,-999/)/)/)
   x@_FillValue = -999

   xmean   = new((/3,2/),float)
   xvar    = new((/3,2/),float)
   xskew   = new((/3,2/),float)
   xkurt   = new((/3,2/),float)
   xmed    = new((/3,2/),float)
   xmrng   = new((/3,2/),float)
   xrng    = new((/3,2/),float)
   xmeant  = new((/3,2/),float)
   xsdt    = new((/3,2/),float)
   npts    = new((/3,2/),integer)   

   stat2(x,xmean,xvar,npts)
   print(xmean)
   print(xvar)
   print(npts)

   stat4(x,xmean,xvar,xskew,xkurt,npts)
   print(xmean)
   print(xvar)
   print(xskew)
   print(xkurt)
   print(npts)

   stat_medrng(x,xmed,xmrng,xrng,npts)
   print(xmed)
   print(xmrng)
   print(xrng)
   print(npts)

   stat_trim(x,0.0,xmeant,xsdt,npts)
   print(xmeant)
   print(xsdt)
   print(npts)
end