comparison toolboxes/FullBNT-1.0.7/KPMtools/chi2inv.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function x = chi2inv(p,v);
+%CHI2INV Inverse of the chi-square cumulative distribution function (cdf).
+%   X = CHI2INV(P,V)  returns the inverse of the chi-square cdf with V  
+%   degrees of freedom at the values in P. The chi-square cdf with V 
+%   degrees of freedom, is the gamma cdf with parameters V/2 and 2.   
+%
+%   The size of X is the common size of P and V. A scalar input
+%   functions as a constant matrix of the same size as the other input.   
+
+%   References:
+%      [1]  M. Abramowitz and I. A. Stegun, "Handbook of Mathematical
+%      Functions", Government Printing Office, 1964, 26.4.
+%      [2] E. Kreyszig, "Introductory Mathematical Statistics",
+%      John Wiley, 1970, section 10.2 (page 144)
+
+%   Copyright 1993-2002 The MathWorks, Inc. 
+%   $Revision: 1.1.1.1 $  $Date: 2005/04/26 02:30:30 $
+
+if nargin < 2, 
+    error('Requires two input arguments.');
+end
+
+[errorcode p v] = distchck(2,p,v);
+
+if errorcode > 0
+    error('Requires non-scalar arguments to match in size.');
+end
+
+% Call the gamma inverse function. 
+x = gaminv(p,v/2,2);
+
+% Return NaN if the degrees of freedom is not positive.
+k = (v <= 0);
+if any(k(:))
+    x(k) = NaN;
+end