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1 ## Copyright (C) 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}] =} mcnemar_test (@var{x}) |
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21 ## For a square contingency table @var{x} of data cross-classified on |
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22 ## the row and column variables, McNemar's test can be used for testing |
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23 ## the null hypothesis of symmetry of the classification probabilities. |
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24 ## |
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25 ## Under the null, @var{chisq} is approximately distributed as chisquare |
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26 ## with @var{df} degrees of freedom. |
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27 ## |
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28 ## The p-value (1 minus the CDF of this distribution at @var{chisq}) is |
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29 ## returned in @var{pval}. |
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30 ## |
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31 ## If no output argument is given, the p-value of the test is displayed. |
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32 ## @end deftypefn |
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33 |
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34 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
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35 ## Description: McNemar's test for symmetry |
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36 |
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37 function [pval, chisq, df] = mcnemar_test (x) |
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38 |
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39 if (nargin != 1) |
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40 print_usage (); |
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41 endif |
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42 |
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43 if (! (min (size (x)) > 1) && issquare (x)) |
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44 error ("mcnemar_test: x must be a square matrix of size > 1"); |
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45 elseif (! (all (all (x >= 0)) && all (all (x == round (x))))) |
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46 error ("mcnemar_test: all entries of x must be nonnegative integers"); |
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47 endif |
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48 |
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49 r = rows (x); |
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50 df = r * (r - 1) / 2; |
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51 if (r == 2) |
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52 num = max (abs (x - x') - 1, 0) .^ 2; |
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53 else |
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54 num = abs (x - x') .^ 2; |
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55 endif |
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56 |
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57 chisq = sum (sum (triu (num ./ (x + x'), 1))); |
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58 pval = 1 - chisquare_cdf (chisq, df); |
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59 |
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60 if (nargout == 0) |
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61 printf (" pval: %g\n", pval); |
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62 endif |
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63 |
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64 endfunction |
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65 |
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66 |
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67 |
