update packages

[CreaPhase.git] / octave_packages / m / statistics / tests / mcnemar_test.m

diff --git a/octave_packages/m/statistics/tests/mcnemar_test.m b/octave_packages/m/statistics/tests/mcnemar_test.m
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+## Copyright (C) 1996-2012 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
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{pval}, @var{chisq}, @var{df}] =} mcnemar_test (@var{x})
+## For a square contingency table @var{x} of data cross-classified on
+## the row and column variables, McNemar's test can be used for testing
+## the null hypothesis of symmetry of the classification probabilities.
+##
+## Under the null, @var{chisq} is approximately distributed as chisquare
+## with @var{df} 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 of the test is displayed.
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@wu-wien.ac.at>
+## Description: McNemar's test for symmetry
+
+function [pval, chisq, df] = mcnemar_test (x)
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+
+  if (! (min (size (x)) > 1) && issquare (x))
+    error ("mcnemar_test: X must be a square matrix of size > 1");
+  elseif (! (all (all (x >= 0)) && all (all (x == fix (x)))))
+    error ("mcnemar_test: all entries of X must be non-negative integers");
+  endif
+
+  r = rows (x);
+  df = r * (r - 1) / 2;
+  if (r == 2)
+    num = max (abs (x - x') - 1, 0) .^ 2;
+  else
+    num = abs (x - x') .^ 2;
+  endif
+
+  chisq = sum (sum (triu (num ./ (x + x'), 1)));
+  pval = 1 - chi2cdf (chisq, df);
+
+  if (nargout == 0)
+    printf ("  pval: %g\n", pval);
+  endif
+
+endfunction
+
+
+