annotate scripts/statistics/distributions/exppdf.m @ 13171:19b9f17d22af

Overhaul of statistical distribution functions Support class "single" 75% reduction in memory usage More Matlab compatibility for corner cases * betacdf.m, betainv.m, betapdf.m, betarnd.m, binocdf.m, binoinv.m, binopdf.m, binornd.m, cauchy_cdf.m, cauchy_inv.m, cauchy_pdf.m, cauchy_rnd.m, chi2cdf.m, chi2inv.m, chi2pdf.m, chi2rnd.m, discrete_cdf.m, discrete_inv.m, discrete_pdf.m, discrete_rnd.m, empirical_cdf.m, empirical_inv.m, empirical_pdf.m, empirical_rnd.m, expcdf.m, expinv.m, exppdf.m, exprnd.m, fcdf.m, finv.m, fpdf.m, frnd.m, gamcdf.m, gaminv.m, gampdf.m, gamrnd.m, geocdf.m, geoinv.m, geopdf.m, geornd.m, hygecdf.m, hygeinv.m, hygepdf.m, hygernd.m, kolmogorov_smirnov_cdf.m, laplace_cdf.m, laplace_inv.m, laplace_pdf.m, laplace_rnd.m, logistic_cdf.m, logistic_inv.m, logistic_pdf.m, logistic_rnd.m, logncdf.m, logninv.m, lognpdf.m, lognrnd.m, nbincdf.m, nbininv.m, nbinpdf.m, nbinrnd.m, normcdf.m, norminv.m, normpdf.m, normrnd.m, poisscdf.m, poissinv.m, poisspdf.m, poissrnd.m, stdnormal_cdf.m, stdnormal_inv.m, stdnormal_pdf.m, stdnormal_rnd.m, tcdf.m, tinv.m, tpdf.m, trnd.m, unidcdf.m, unidinv.m, unidpdf.m, unidrnd.m, unifcdf.m, unifinv.m, unifpdf.m, unifrnd.m, wblcdf.m, wblinv.m, wblpdf.m, wblrnd.m: Return "single" outputs for "single" inputs, Use logical indexing rather than find() for 75% memory savings, Add tests for all functions, Use consistent documentation across all functions, More Matlab compatibilitcy for corner cases.
author Rik <octave@nomad.inbox5.com>
date Tue, 20 Sep 2011 12:13:13 -0700
parents aa3ba343a76f
children 72c96de7a403
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1 ## Copyright (C) 2011 Rik Wehbring
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2 ## Copyright (C) 1995-2011 Kurt Hornik
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3 ##
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4 ## This file is part of Octave.
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5 ##
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6 ## Octave is free software; you can redistribute it and/or modify it
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7 ## under the terms of the GNU General Public License as published by
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8 ## the Free Software Foundation; either version 3 of the License, or (at
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9 ## your option) any later version.
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10 ##
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11 ## Octave is distributed in the hope that it will be useful, but
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 ## General Public License for more details.
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15 ##
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16 ## You should have received a copy of the GNU General Public License
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17 ## along with Octave; see the file COPYING. If not, see
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18 ## <http://www.gnu.org/licenses/>.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {Function File} {} exppdf (@var{x}, @var{lambda})
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22 ## For each element of @var{x}, compute the probability density function
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23 ## (PDF) at @var{x} of the exponential distribution with mean @var{lambda}.
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24 ## @end deftypefn
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25
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26 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
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27 ## Description: PDF of the exponential distribution
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28
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29 function pdf = exppdf (x, lambda)
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30
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31 if (nargin != 2)
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32 print_usage ();
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33 endif
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34
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35 if (!isscalar (lambda))
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36 [retval, x, lambda] = common_size (x, lambda);
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37 if (retval > 0)
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38 error ("exppdf: X and LAMBDA must be of common size or scalars");
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39 endif
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40 endif
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41
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42 if (iscomplex (x) || iscomplex (lambda))
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43 error ("exppdf: X and LAMBDA must not be complex");
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44 endif
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45
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46 if (isa (x, "single") || isa (lambda, "single"))
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47 pdf = zeros (size (x), "single");
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48 else
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49 pdf = zeros (size (x));
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50 endif
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51
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52 k = isnan (x) | !(lambda > 0);
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53 pdf(k) = NaN;
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55 k = (x >= 0) & (x < Inf) & (lambda > 0);
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56 if isscalar (lambda)
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57 pdf(k) = exp (- x(k) / lambda) / lambda;
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58 else
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59 pdf(k) = exp (- x(k) ./ lambda(k)) ./ lambda(k);
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60 endif
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61
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62 endfunction
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64
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65 %!shared x,y
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66 %! x = [-1 0 0.5 1 Inf];
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67 %! y = gampdf (x, 1, 2);
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68 %!assert(exppdf (x, 2*ones(1,5)), y);
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69 %!assert(exppdf (x, 2*[1 0 NaN 1 1]), [y(1) NaN NaN y(4:5)]);
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70 %!assert(exppdf ([x, NaN], 2), [y, NaN]);
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71
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72 %% Test class of input preserved
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73 %!assert(exppdf (single([x, NaN]), 2), single([y, NaN]));
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74 %!assert(exppdf ([x, NaN], single(2)), single([y, NaN]));
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75
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76 %% Test input validation
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77 %!error exppdf ()
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78 %!error exppdf (1)
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79 %!error exppdf (1,2,3)
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80 %!error exppdf (ones(3),ones(2))
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81 %!error exppdf (ones(2),ones(3))
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82 %!error exppdf (i, 2)
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83 %!error exppdf (2, i)
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84