update packages

[CreaPhase.git] / octave_packages / m / statistics / distributions / logistic_pdf.m

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+## Copyright (C) 1995-2012 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} {} logistic_pdf (@var{x})
+## For each element of @var{x}, compute the PDF at @var{x} of the
+## logistic distribution.
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@wu-wien.ac.at>
+## Description: PDF of the logistic distribution
+
+function pdf = logistic_pdf (x)
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+
+  if (iscomplex (x))
+    error ("logistic_pdf: X must not be complex");
+  endif
+
+  cdf = logistic_cdf (x);
+  pdf = cdf .* (1 - cdf);
+
+endfunction
+
+
+%!shared x,y
+%! x = [-Inf -log(4) 0 log(4) Inf];
+%! y = [0, 0.16, 1/4, 0.16, 0]; 
+%!assert(logistic_pdf ([x, NaN]), [y, NaN], eps);
+
+%% Test class of input preserved
+%!assert(logistic_pdf (single([x, NaN])), single([y, NaN]), eps ("single"));
+
+%% Test input validation
+%!error logistic_pdf ()
+%!error logistic_pdf (1,2)
+%!error logistic_pdf (i)
+