plegendre.m

来自「模式识别工具包」· M 代码 · 共 45 行

%	plegendre	- Legendre polynomial
%
%	[pvalue]	= plegendre(j,x)
%
%	_____OUTPUTS____________________________________________________________
%	pvalue	polynomial expansion corresponding to x(xwant)	(col vectors)
%
%	_____INPUTS_____________________________________________________________
%	j	degree						(scalar)
%	x	independent scalars				(row vector)
%
%	_____SEE ALSO___________________________________________________________
%	
%
%	(C) 1998.04.22 Kui-yu Chang
%	http://lans.ece.utexas.edu/~kuiyu

%	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, write to the Free Software
%	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
%	or check
%			http://www.gnu.org/

function	[pvalue]	= plegendre(j,x)

if j==0
	pvalue	= ones(size(x));
elseif j==1
	pvalue	= x;
else
	num	= (2*j-1)*x.*plegendre(j-1,x)-(j-1)*plegendre(j-2,x);
	pvalue	= num/j;
end