2 % TPDF returns student probability density
6 % Computes the PDF of a the student distribution
7 % with DF degreas of freedom
8 % x,DF must be matrices of same size, or any one can be a scalar.
10 % see also: TINV, TCDF, NORMPDF, NORMCDF, NORMINV
14 % $Id: tpdf.m 9033 2011-11-08 20:58:07Z schloegl $
15 % Copyright (C) 2000-2003,2008,2009,2010 by Alois Schloegl <alois.schloegl@gmail.com>
16 % This function is part of the NaN-toolbox
17 % http://pub.ist.ac.at/~schloegl/matlab/NaN/
19 % This program is free software; you can redistribute it and/or modify
20 % it under the terms of the GNU General Public License as published by
21 % the Free Software Foundation; either version 2 of the License, or
22 % (at your option) any later version.
24 % This program is distributed in the hope that it will be useful,
25 % but WITHOUT ANY WARRANTY; without even the implied warranty of
26 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
27 % GNU General Public License for more details.
29 % You should have received a copy of the GNU General Public License
30 % along with this program; If not, see <http://www.gnu.org/licenses/>.
32 % allocate memory and check size of arguments
33 p = x+n; % if this line causes an error, size of input arguments do not fit.
34 ix = (n>0) & (n~=inf) & ~isnan(x);
36 % make size of x and n equal
40 % workaround for invalid arguments in BETA
42 p(ix) = (exp (-(n(ix)+1).*log(1+x(ix).^2./n(ix))/2) ./ (sqrt(n(ix)).* beta(n(ix)/2, 1/2)));
47 p = reshape(p,size(x));
49 %!assert(tpdf(NaN,4),NaN)