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annotate scripts/statistics/tests/chisquare_test_independence.m @ 3426:f8dde1807dee

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[project @ 2000-01-13 08:40:00 by jwe]
author jwe
date Thu, 13 Jan 2000 08:40:53 +0000
parents 041ea33fbbf4
children d8b731d3f7a3
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1 ## Copyright (C) 1995, 1996, 1997 Kurt Hornik
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2 ##
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3 ## This program is free software; you can redistribute it and/or modify
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4 ## it under the terms of the GNU General Public License as published by
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5 ## the Free Software Foundation; either version 2, or (at your option)
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6 ## any later version.
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7 ##
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8 ## This program is distributed in the hope that it will be useful, but
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9 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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11 ## General Public License for more details.
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12 ##
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13 ## You should have received a copy of the GNU General Public License
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14 ## along with this file. If not, write to the Free Software Foundation,
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15 ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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17 ## usage: [pval, chisq, df] = chisquare_test_independence (X)
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18 ##
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19 ## Perform a chi-square test for indepence based on the contingency
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20 ## table X.
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21 ##
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22 ## Under the null hypothesis of independence, chisq approximately has a
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23 ## chi-square distribution with df degrees of freedom. pval is the
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24 ## p-value (1 minus the CDF of this distribution at chisq) of the test.
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25 ##
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26 ## If no output argument is given, the p-value is displayed.
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28 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
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29 ## Description: Chi-square test for independence
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30
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31 function [pval, chisq, df] = chisquare_test_independence (X)
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33 if (nargin != 1)
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34 usage ("chisquare_test_independence (X)");
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35 endif
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37 [r, s] = size (X);
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38 df = (r - 1) * (s - 1);
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39 n = sum (sum (X));
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40 Y = sum (X')' * sum (X) / n;
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41 X = (X - Y) .^2 ./ Y;
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42 chisq = sum (sum (X));
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43 pval = 1 - chisquare_cdf (chisq, df);
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44
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45 if (nargout == 0)
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46 printf(" pval: %g\n", pval);
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47 endif
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48
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49 endfunction