posdef.m

文件是编辑好的m文件

function s=posdef(Q)
% 确定矩阵Q的正定性

% Copyright 2001-2002 ECUST. 
%   $Revision: 1.2 $  $Date: 2002/02/24 11:02:32 $

r=length(Q);for i=1:r;qq(i)=det(Q(1:i,1:i)),end
k=find(qq<0);j=find(qq==0);
if isempty(j) &isempty(k),s='matrix is positive definite matrix',
elseif  isempty(k),s='matrix is half positive definite matrix',
else s='non-definite matrix',end;