Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/~rminchin/idl/medabsdev.pro Дата изменения: Tue Oct 23 17:47:50 2012 Дата индексирования: Sun Apr 10 04:37:28 2016 Кодировка:

; Modification of IDL built-in meanabsdev to give median absolute
; deviation rather than mean absolute deviation
;
; Usage as for meanabsdev (see below)

;$Id: meanabsdev.pro,v 1.5.4.1 1999/01/16 16:42:47 scottm Exp $
;
; Copyright (c) 1997-1999, Research Systems, Inc. All rights reserved.
; Unauthorized reproduction prohibited.
;+
; NAME:
; MeanAbsDev
;
; PURPOSE:
; MeanAbsDev computes the mean absolute deviation (average
; deviation) of an N-element vector.
;
; CATEGORY:
; Statistics.
;
; CALLING SEQUENCE:
; Result = MeanAbsDev(X)
;
; INPUTS:
; X: An N-element vector of type integer, float or double.
;
; KEYWORD PARAMETERS:
;
; DOUBLE: If set to a non-zero value, MEANABSDEV performs its
; computations in double precision arithmetic and returns
; a double precision result. If not set to a non-zero value,
; the computations and result depend upon the type of the
; input data (integer and float data return float results,
; while double data returns double results). This has no
; effect if the Median keyword is set.
;
; MEDIAN: If set to a non-zero value, meanabsdev will return
; the average deviation from the median, rather than
; the mean. If Median is not set, meanabsdev will return
; the average deviation from the mean.
;
; NAN: If set, treat NaN data as missing.
;
; EXAMPLES:
; Define the N-element vector of sample data.
; x = [1, 1, 1, 2, 5]
; Compute the average deviation from the mean.
; result = MeanAbsDev( x )
; The result should be:
; 1.20000
;
; Compute the average deviation from the median.
; result = MeanAbsDev( x, /median )
; The result should be:
; 1.00000
;
; PROCEDURE:
; MeanAbsDev calls the IDL function MEAN.
;
; MeanAbsDev calls the IDL function MEDIAN if the Median
; keyword is set to a nonzero value.
;
; REFERENCE:
; APPLIED STATISTICS (third edition)
; J. Neter, W. Wasserman, G.A. Whitmore
; ISBN 0-205-10328-6
;
; MODIFICATION HISTORY:
; Written by: GSL, RSI, August 1997
; RJF, RSI, Sep 1998, Removed NaN keyword from Median call
; as NaN is not currently supported by
; the Median routine.
;-
FUNCTION MedAbsDev, X, Double = Double, Median = Median, NaN = NaN

ON_ERROR, 2
IF keyword_set( Median ) THEN BEGIN

IF keyword_set( NaN ) THEN BEGIN
whereNotNaN = where( finite(X) ne 0, nanCount)
IF nanCount GT 0 THEN BEGIN
middle = median( X[whereNotNan],double=double, /even )
END ELSE BEGIN
middle = 0 ; Let MOMENT throw the error...
END
END ELSE BEGIN
middle = median( X,double=double, /even )
END

END ELSE BEGIN

middle = mean( X, Double=Double, NaN = NaN )

END

RETURN, median( abs( X - middle ),double=double,/even)
END