Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / nan-2.5.5 / tpdf.m

diff --git a/octave_packages/nan-2.5.5/tpdf.m b/octave_packages/nan-2.5.5/tpdf.m
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+++ b/octave_packages/nan-2.5.5/tpdf.m
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+function p = tpdf(x,n)
+% TPDF returns student probability density 
+%
+% pdf = tpdf(x,DF);
+%
+% Computes the PDF of a the student distribution 
+%    with DF degreas of freedom
+% x,DF must be matrices of same size, or any one can be a scalar. 
+%
+% see also: TINV, TCDF, NORMPDF, NORMCDF, NORMINV 
+
+% Reference(s):
+
+%      $Id: tpdf.m 9033 2011-11-08 20:58:07Z schloegl $
+%      Copyright (C) 2000-2003,2008,2009,2010 by Alois Schloegl <alois.schloegl@gmail.com>     
+%       This function is part of the NaN-toolbox
+%       http://pub.ist.ac.at/~schloegl/matlab/NaN/
+
+%    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 2 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/>.
+
+% allocate memory and check size of arguments
+p = x+n;         % if this line causes an error, size of input arguments do not fit. 
+ix = (n>0) & (n~=inf) & ~isnan(x); 
+
+% make size of x and n equal
+n = x+n-x;
+x = x+n-n;
+
+% workaround for invalid arguments in BETA
+if any(ix)
+p(ix) = (exp (-(n(ix)+1).*log(1+x(ix).^2./n(ix))/2) ./ (sqrt(n(ix)).* beta(n(ix)/2, 1/2)));
+end; 
+p(~ix)= NaN;
+
+% shape output
+p = reshape(p,size(x));
+
+%!assert(tpdf(NaN,4),NaN)