How to find certain index of a diagonal matrix , when a condition meets?

Question

Rida 2014-4-25

评论： Azzi Abdelmalek 2014-4-25

I have the following code:

covar = 1.0/m .* X' * X; % computing co-variance

[U, S, V] = svd(covar); % singular value decomposition % U contains principal components and V contains diagonal matrix

% %% % % ===== Dimensioanlity Reduction Finding K for projection======

s3=sum (diag(S));

sum1=0;

temp1=0;

for j=1:length(S)

    sum1=sum1+S(j,j);
    div_res=(sum1/s3);
    if(div_res==0.9)
    index=find(j) ; 
    end
end

All I want is, that value of "j" when the div_res=>0.9 but I am not getting the correct answer

Answer 1

Azzi Abdelmalek 2014-4-25

n=size(A,1);
idx=find(A(sub2ind([n n],1:n,1:n))>=0.9)

Azzi Abdelmalek 2014-4-25

That depends on how many times the condition is met