function x=isPositiveDefinite(A)
%Function to check whether a given matrix A is positive definite
 
%Author Mathuranathan for http://www.gaussianwaves.com
 
%Licensed under Creative Commons: CC-NC-BY-SA 3.0
 
%Returns x=1, if the input matrix is positive definite
 
%Returns x=0, if the input matrix is not positive definite
 
%Throws error if the input matrix is not symmetric
 
 
    %Check if the matrix is symmetric
    [m,n]=size(A); 
    if m~=n,
        error('A não é Simétrica');
    end
    
    %Test for positive definiteness
    x=1; %Flag to check for positiveness
    for i=1:m
        subA=A(1:i,1:i); %Extract upper left kxk submatrix
        if(det(subA)<=0); %Check if the determinent of the kxk submatrix is +ve
            x=0;
            break;
        end
    end
    %For debug
    %if x
    %    display('Given Matrix is Positive definite');
    %else
    %    display('Given Matrix is NOT positive definite');
    %end    
end