/usr/share/octave/packages/statistics-1.2.3/vmpdf.m is in octave-statistics 1.2.3-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | ## Copyright (C) 2009 Soren Hauberg <soren@hauberg.org>
##
## This program 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.
##
## This program 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
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} @var{theta} = vmpdf (@var{x}, @var{mu}, @var{k})
## Evaluates the Von Mises probability density function.
##
## The Von Mises distribution has probability density function
## @example
## f (@var{x}) = exp (@var{k} * cos (@var{x} - @var{mu})) / @var{Z} ,
## @end example
## where @var{Z} is a normalisation constant. By default, @var{mu} is 0 and
## @var{k} is 1.
## @seealso{vmrnd}
## @end deftypefn
function p = vmpdf (x, mu = 0, k = 1)
## Check input
if (!isreal (x))
error ("vmpdf: first input must be real");
endif
if (!isreal (mu))
error ("vmpdf: second input must be a scalar");
endif
if (!isreal (k) || k <= 0)
error ("vmpdf: third input must be a real positive scalar");
endif
## Evaluate PDF
Z = 2 * pi * besseli (0, k);
p = exp (k * cos (x-mu)) / Z;
endfunction
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