how to take the non zero values from one matrix and put them in another??

I have a matrix [640 640] with few non zero values and many zeros. I want to put all the non zero values in a new matrix. Something like:

for i=1:640

 for j=1:640

if A(i,j)~=0

B(i,j)=A(i,j)
   end

end

end

But this doesn't work.. Any suggestions?

[Fangjun Jiang]

What do you mean doesn't work. There is an easy way to do it which uses logic index. What value do you want for other elements in B?

Answer 1

[Fangjun Jiang]

    B=A(A~=0);

Answer 2

[Florin Neacsu]

Try :

ind1=A~=0;
B(ind1)=A(ind1);

Regards, Florin

[Fangjun Jiang]

For this particular case, B would be the same as A.