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annotate scripts/statistics/models/logistic_regression_derivatives.m @ 5307:4c8a2e4e0717

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[project @ 2005-04-26 19:24:27 by jwe]
author jwe
date Tue, 26 Apr 2005 19:24:47 +0000
parents 38c61cbf086c
children 2a16423e4aa0
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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 2, or (at your option)
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8 ## 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, write to the Free
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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18 ## 02110-1301, USA.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {Function File} {[@var{dl}, @var{d2l}] =} logistic_regression_derivatives (@var{x}, @var{z}, @var{z1}, @var{g}, @var{g1}, @var{p})
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22 ## Called by logistic_regression. Calculates derivates of the
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23 ## log-likelihood for ordinal logistic regression model.
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24 ## @end deftypefn
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26 ## Author: Gordon K. Smyth <gks@maths.uq.oz.au>
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27 ## Adapted-By: KH <Kurt.Hornik@ci.tuwien.ac.at>
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28 ## Description: Derivates of log-likelihood in logistic regression
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29
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30 function [dl, d2l] = logistic_regression_derivatives (x, z, z1, g, g1, p)
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31
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32 ## first derivative
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33 v = g .* (1 - g) ./ p; v1 = g1 .* (1 - g1) ./ p;
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34 dlogp = [(dmult (v, z) - dmult (v1, z1)), (dmult (v - v1, x))];
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35 dl = sum (dlogp)';
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36
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37 ## second derivative
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38 w = v .* (1 - 2 * g); w1 = v1 .* (1 - 2 * g1);
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39 d2l = [z, x]' * dmult (w, [z, x]) - [z1, x]' * dmult (w1, [z1, x]) ...
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40 - dlogp' * dlogp;
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41
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42 endfunction