## Copyright (C) 1995, 1996, 1997  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 2, 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, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.

## -*- texinfo -*-
## @deftypefn {Function File} {} laplace_cdf (@var{x})
## For each element of @var{x}, compute the cumulative distribution
## function (CDF) at @var{x} of the Laplace distribution.
## @end deftypefn

## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
## Description: CDF of the Laplace distribution

function cdf = laplace_cdf (x)

  if (nargin != 1)
    usage ("laplace_cdf (x)");
  endif

  [r, c] = size (x);
  s = r * c;
  x = reshape (x, 1, s);
  cdf = zeros (1, s);

  k = find (isnan (x));
  if (any (k))
    cdf(k) = NaN * ones (1, length (k));
  endif

  k = find (x == Inf);
  if (any (k))
    cdf(k) = ones (1, length (k));
  endif

  k = find ((x > -Inf) & (x < Inf));
  if (any (k))
    cdf(k) = (1 + sign (x(k)) .* (1 - exp (- abs (x(k))))) / 2;
  endif

  cdf = reshape (cdf, r, c);

endfunction