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annotate scripts/statistics/tests/chisquare_test_independence.m @ 7016:93c65f2a5668

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[project @ 2007-10-12 06:40:56 by jwe]
author jwe
date Fri, 12 Oct 2007 06:41:26 +0000
parents 8b0cfeb06365
children a1dbe9d80eee
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1 ## Copyright (C) 1995, 1996, 1997 Kurt Hornik
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2 ##
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3 ## This file is part of Octave.
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4 ##
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5 ## Octave is free software; you can redistribute it and/or modify it
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6 ## under the terms of the GNU General Public License as published by
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7 ## the Free Software Foundation; either version 3 of the License, or (at
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8 ## your option) any later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 ## General Public License for more details.
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14 ##
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15 ## You should have received a copy of the GNU General Public License
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16 ## along with Octave; see the file COPYING. If not, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Function File} {[@var{pval}, @var{chisq}, @var{df}] =} chisquare_test_independence (@var{x})
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21 ## Perform a chi-square test for independence based on the contingency
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22 ## table @var{x}. Under the null hypothesis of independence,
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23 ## @var{chisq} approximately has a chi-square distribution with
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24 ## @var{df} degrees of freedom.
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25 ##
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26 ## The p-value (1 minus the CDF of this distribution at chisq) of the
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27 ## test is returned in @var{pval}.
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28 ##
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29 ## If no output argument is given, the p-value is displayed.
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30 ## @end deftypefn
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32 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
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33 ## Description: Chi-square test for independence
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35 function [pval, chisq, df] = chisquare_test_independence (X)
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37 if (nargin != 1)
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38 print_usage ();
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39 endif
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41 [r, s] = size (X);
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42 df = (r - 1) * (s - 1);
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43 n = sum (sum (X));
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44 Y = sum (X')' * sum (X) / n;
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45 X = (X - Y) .^2 ./ Y;
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46 chisq = sum (sum (X));
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47 pval = 1 - chisquare_cdf (chisq, df);
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49 if (nargout == 0)
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50 printf(" pval: %g\n", pval);
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51 endif
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53 endfunction