X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Fm%2Fstatistics%2Ftests%2Fchisquare_test_homogeneity.m;fp=octave_packages%2Fm%2Fstatistics%2Ftests%2Fchisquare_test_homogeneity.m;h=8cf32bff266223fa70087958137d741e6f9102c6;hp=0000000000000000000000000000000000000000;hb=1c0469ada9531828709108a4882a751d2816994a;hpb=63de9f36673d49121015e3695f2c336ea92bc278
diff --git a/octave_packages/m/statistics/tests/chisquare_test_homogeneity.m b/octave_packages/m/statistics/tests/chisquare_test_homogeneity.m
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+## Copyright (C) 1995-2012 Kurt Hornik
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING. If not, see
+## .
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{pval}, @var{chisq}, @var{df}] =} chisquare_test_homogeneity (@var{x}, @var{y}, @var{c})
+## Given two samples @var{x} and @var{y}, perform a chisquare test for
+## homogeneity of the null hypothesis that @var{x} and @var{y} come from
+## the same distribution, based on the partition induced by the
+## (strictly increasing) entries of @var{c}.
+##
+## For large samples, the test statistic @var{chisq} approximately follows a
+## chisquare distribution with @var{df} = @code{length (@var{c})}
+## degrees of freedom.
+##
+## The p-value (1 minus the CDF of this distribution at @var{chisq}) is
+## returned in @var{pval}.
+##
+## If no output argument is given, the p-value is displayed.
+## @end deftypefn
+
+## Author: KH
+## Description: Chi-square test for homogeneity
+
+function [pval, chisq, df] = chisquare_test_homogeneity (x, y, c)
+
+ if (nargin != 3)
+ print_usage ();
+ endif
+
+ if (! (isvector(x) && isvector(y) && isvector(c)))
+ error ("chisquare_test_homogeneity: X, Y and C must be vectors");
+ endif
+ ## Now test c for strictly increasing entries
+ df = length (c);
+ if (any ((c(2 : df) - c(1 : (df - 1))) <= 0))
+ error ("chisquare_test_homogeneity: C must be increasing");
+ endif
+
+ c = [(reshape (c, 1, df)), Inf];
+ l_x = length (x);
+ x = reshape (x, l_x, 1);
+ n_x = sum (x * ones (1, df+1) < ones (l_x, 1) * c);
+ l_y = length (y);
+ y = reshape (y, l_y, 1);
+ n_y = sum(y * ones (1, df+1) < ones (l_y, 1) * c);
+ chisq = l_x * l_y * sum ((n_x/l_x - n_y/l_y).^2 ./ (n_x + n_y));
+ pval = 1 - chi2cdf (chisq, df);
+
+ if (nargout == 0)
+ printf(" pval: %g\n", pval);
+ endif
+
+endfunction