camir-aes2014: toolboxes/FullBNT-1.0.7/KPMtools/chi2inv.m annotate

first hg version after svn

rev	line source
wolffd@0	1 function x = chi2inv(p,v);
wolffd@0	2 %CHI2INV Inverse of the chi-square cumulative distribution function (cdf).
wolffd@0	3 % X = CHI2INV(P,V) returns the inverse of the chi-square cdf with V
wolffd@0	4 % degrees of freedom at the values in P. The chi-square cdf with V
wolffd@0	5 % degrees of freedom, is the gamma cdf with parameters V/2 and 2.
wolffd@0	6 %
wolffd@0	7 % The size of X is the common size of P and V. A scalar input
wolffd@0	8 % functions as a constant matrix of the same size as the other input.
wolffd@0	9
wolffd@0	10 % References:
wolffd@0	11 % [1] M. Abramowitz and I. A. Stegun, "Handbook of Mathematical
wolffd@0	12 % Functions", Government Printing Office, 1964, 26.4.
wolffd@0	13 % [2] E. Kreyszig, "Introductory Mathematical Statistics",
wolffd@0	14 % John Wiley, 1970, section 10.2 (page 144)
wolffd@0	15
wolffd@0	16 % Copyright 1993-2002 The MathWorks, Inc.
wolffd@0	17 % $Revision: 1.1.1.1 $ $Date: 2005/04/26 02:30:30 $
wolffd@0	18
wolffd@0	19 if nargin < 2,
wolffd@0	20 error('Requires two input arguments.');
wolffd@0	21 end
wolffd@0	22
wolffd@0	23 [errorcode p v] = distchck(2,p,v);
wolffd@0	24
wolffd@0	25 if errorcode > 0
wolffd@0	26 error('Requires non-scalar arguments to match in size.');
wolffd@0	27 end
wolffd@0	28
wolffd@0	29 % Call the gamma inverse function.
wolffd@0	30 x = gaminv(p,v/2,2);
wolffd@0	31
wolffd@0	32 % Return NaN if the degrees of freedom is not positive.
wolffd@0	33 k = (v <= 0);
wolffd@0	34 if any(k(:))
wolffd@0	35 x(k) = NaN;
wolffd@0	36 end

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