volsphere.m

来自「数据挖掘的工具箱,最新版的,希望对做这方面研究的人有用」· M 代码 · 共 30 行

function V = volsphere(d,R,takelog)
%VOLSPHERE Compute the volume of a hypersphere
%
%      V = VOLSPHERE(D,R)
%
% Compute the volume of a hypersphere in D dimensions, with radius R.
%
%      V = VOLSPHERE(D,R,TAKELOG)
%
% If TAKELOG>0 than the log(V) is computed (more useful for high
% dimensions)
%
% Default: R=1; TAKELOG=0


if nargin<3
	takelog=0;
end
if nargin<2
	R = 1;
end

if takelog
	V = log(2) + d*log(R*sqrt(pi)) - log(d) - gammaln(d/2);
else
	V = 2*(R*sqrt(pi))^d/(d*gamma(d/2));
end

return