STANDARDIZE

The STANDARDIZE function computes standardized variables from an array of m variables (columns) and n observations (rows).

This routine is written in the IDL language. Its source code can be found in the file standardize.pro in the lib subdirectory of the IDL distribution.

Examples

; Define an array with 4 variables and 20 observations:
array = $
           [[19.5, 43.1, 29.1, 11.9], $
            [24.7, 49.8, 28.2, 22.8], $
            [30.7, 51.9, 37.0, 18.7], $
            [29.8, 54.3, 31.1, 20.1], $
            [19.1, 42.2, 30.9, 12.9], $
            [25.6, 53.9, 23.7, 21.7], $
            [31.4, 58.5, 27.6, 27.1], $
            [27.9, 52.1, 30.6, 25.4], $
            [22.1, 49.9, 23.2, 21.3], $
            [25.5, 53.5, 24.8, 19.3], $
            [31.1, 56.6, 30.0, 25.4], $
            [30.4, 56.7, 28.3, 27.2], $
            [18.7, 46.5, 23.0, 11.7], $
            [19.7, 44.2, 28.6, 17.8], $
            [14.6, 42.7, 21.3, 12.8], $
            [29.5, 54.4, 30.1, 23.9], $
            [27.7, 55.3, 25.7, 22.6], $
            [30.2, 58.6, 24.6, 25.4], $
            [22.7, 48.2, 27.1, 14.8], $
            [25.2, 51.0, 27.5, 21.1]]

Then do the computations and print the results:

; Compute the mean and variance of each variable using the MOMENT 
; function. The skewness and kurtosis are also computed:
FOR K = 0, 3 DO PRINT, MOMENT(array[K,*])
; Compute the standardized variables:
result = STANDARDIZE(array)
; Compute the mean and variance of each standardized variable using 
; the MOMENT function. The skewness and kurtosis are also computed:
FOR K = 0, 3 DO PRINT, MOMENT(result[K,*])

IDL prints:

25.3050      25.2331    -0.454763     -1.10028

51.1700      27.4012    -0.356958     -1.19516

27.6200      13.3017     0.420289     0.104912

20.1950      26.0731    -0.363277     -1.24886

-7.67130e-07      1.00000    -0.454761    -1.10028

-3.65451e-07      1.00000    -0.356958    -1.19516

-1.66707e-07      1.00000     0.420290     0.104913

 4.21703e-07      1.00000    -0.363278    -1.24886

Syntax

Result = STANDARDIZE( A [, /DOUBLE] [, /MEAN=variable] [,/ STDDEV=variable)

Return Value

The result is an m-column, n-row array where all columns have a mean of zero and a variance of one.

Arguments

A

An m-column, n-row single- or double-precision floating-point array.

Keywords

DOUBLE

Set this keyword to force the computation to be done in double-precision arithmetic.

MEAN

Set this keyword to a named variable to return an m-element vector containing the mean of each column of data.

STDDEV

Set this keyword to a named variable to return a m-element vector containing the standard deviation of each column of data.

Version History

5.0	Introduced
8.3	Added MEAN and STDDEV keywords