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[project @ 2002-05-01 06:48:35 by jwe]
author jwe
date Wed, 01 May 2002 06:48:36 +0000
parents 434790acb067
children 265d566cc770
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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, 59 Temple Place - Suite 330, Boston, MA
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18 ## 02111-1307, USA.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {Function File} {} exponential_cdf (@var{x}, @var{lambda})
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22 ## For each element of @var{x}, compute the cumulative distribution
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23 ## function (CDF) at @var{x} of the exponential distribution with
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24 ## parameter @var{lambda}.
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25 ##
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26 ## The arguments can be of common size or scalar.
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27 ## @end deftypefn
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28
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29 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
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30 ## Description: CDF of the exponential distribution
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31
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32 function cdf = exponential_cdf (x, l)
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33
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34 if (nargin != 2)
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35 usage ("exponential_cdf (x, lambda)");
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36 endif
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37
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38 [retval, x, l] = common_size (x, l);
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39 if (retval > 0)
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40 error ("exponential_cdf: x and lambda must be of common size or scalar");
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41 endif
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42
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43 [r, c] = size (x);
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44 s = r * c;
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45 x = reshape (x, 1, s);
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46 l = reshape (l, 1, s);
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47 cdf = zeros (1, s);
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48
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49 k = find (isnan (x) | !(l > 0));
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50 if (any (k))
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51 cdf(k) = NaN * ones (1, length (k));
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52 endif
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53
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54 k = find ((x == Inf) & (l > 0));
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55 if (any (k))
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56 cdf(k) = ones (1, length (k));
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57 endif
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58
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59 k = find ((x > 0) & (x < Inf) & (l > 0));
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60 if (any (k))
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61 cdf (k) = 1 - exp (- l(k) .* x(k));
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62 endif
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63
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64 cdf = reshape (cdf, r, c);
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65
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66 endfunction