1 ## Copyright (C) 2012 Rik Wehbring
2 ## Copyright (C) 1995-2012 Kurt Hornik
4 ## This file is part of Octave.
6 ## Octave is free software; you can redistribute it and/or modify it
7 ## under the terms of the GNU General Public License as published by
8 ## the Free Software Foundation; either version 3 of the License, or (at
9 ## your option) any later version.
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of
13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 ## General Public License for more details.
16 ## You should have received a copy of the GNU General Public License
17 ## along with Octave; see the file COPYING. If not, see
18 ## <http://www.gnu.org/licenses/>.
21 ## @deftypefn {Function File} {} laplace_pdf (@var{x})
22 ## For each element of @var{x}, compute the probability density function
23 ## (PDF) at @var{x} of the Laplace distribution.
26 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
27 ## Description: PDF of the Laplace distribution
29 function pdf = laplace_pdf (x)
36 error ("laplace_pdf: X must not be complex");
39 pdf = exp (- abs (x)) / 2;
45 %! x = [-Inf -log(2) 0 log(2) Inf];
46 %! y = [0, 1/4, 1/2, 1/4, 0];
47 %!assert(laplace_pdf ([x, NaN]), [y, NaN]);
49 %% Test class of input preserved
50 %!assert(laplace_pdf (single([x, NaN])), single([y, NaN]));
52 %% Test input validation
53 %!error laplace_pdf ()
54 %!error laplace_pdf (1,2)
55 %!error laplace_pdf (i)