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annotate scripts/statistics/distributions/logistic_inv.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 265d566cc770
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} {} logistic_inv (@var{x})
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22 ## For each component of @var{x}, compute the quantile (the inverse of
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23 ## the CDF) at @var{x} of the logistic distribution.
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24 ## @end deftypefn
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25
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26 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
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27 ## Description: Quantile function of the logistic distribution
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28
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29 function inv = logistic_inv (x)
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30
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31 if (nargin != 1)
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32 usage ("logistic_inv (x)");
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33 endif
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34
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35 inv = zeros (size (x));
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36
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37 k = find ((x < 0) | (x > 1) | isnan (x));
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38 if (any (k))
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39 inv(k) = NaN;
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40 endif
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41
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42 k = find (x == 0);
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43 if (any (k))
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44 inv(k) = -Inf;
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45 endif
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46
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47 k = find (x == 1);
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48 if (any (k))
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49 inv(k) = Inf;
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50 endif
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51
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52 k = find ((x > 0) & (x < 1));
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53 if (any (k))
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54 inv (k) = - log (1 ./ x(k) - 1);
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55 endif
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56
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57 endfunction