variance.m

来自「很多通信系统的matlab程序,便于修改调用」· M 代码 · 共 20 行

function v=variance(funfcn,a,b,tol,p1,p2,p3)  %#ok - evals used
%VARIANCE Finds the variance of a random variable 
%	   with probability density function 'funfcn' and 
%	   support [a,b].
% 	   Y=VARIANCE('F',A,B,TOL,P1,P2,P3), finds the variance 
% 	   of the density function F defined in an m-file. The
% 	   function can contain up to three parameters,P1,P2,P3.
%	   tol=the relative error.

args=[];
for n=1:nargin-4
  args=[args,',p',int2str(n)];  
end
args=[args,')']; 
funfcn1=['x.*',funfcn]; % Define x*funfcn
e = eval(['quad(@(x)(' funfcn1 '(x' args '), a, b, tol, [])']); % Find E[X]
newfun=['(x-(',num2str(e),')).^2.*',funfcn]; %Define (X-E(X))^2*funfcn
v = eval(['quad(@(x)(' newfun '(x' args '), a, b, tol, [])']); %Find VAR(X)