normpdf.m

来自「matlab数字信号处理工具箱」· M 代码 · 共 53 行

function p = normpdf(x,m,s);
% NORMPDF returns normal probability density 
%
% pdf = normpdf(x,m,s);
%
% Computes the PDF of a the normal distribution 
%    with mean m and standard deviation s
%    default: m=0; s=1;
% x,m,s must be matrices of same size, or any one can be a scalar. 
%
% see also: NORMCDF, NORMINV 

% Reference(s):

%	$Revision: 1.6 $
%	$Id: normpdf.m,v 1.6 2003/03/13 16:00:33 schloegl Exp $
%	Version 1.28   Date: 13 Mar 2003
%	Copyright (c) 2000-2003 by  Alois Schloegl <[e-mail]>	

%    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

if nargin==1,
        m=0;s=1;
elseif nargin==2,
        s=1;
end;        

% allocate output memory and check size of argument
z = (x-m)./s;		% if this line causes an error, input arguments do not fit. 

%p = ((2*pi)^(-1/2))*exp(-z.^2/2)./s;
SQ2PI = 2.5066282746310005024157652848110;
p = exp(-z.^2/2)./(s*SQ2PI);

p((x==m) & (s==0)) = inf;

p(isinf(z)~=0) = 0;

p(isnan(x) | isnan(m) | isnan(s) | (s<0)) = nan;