How can i replace all positive values of a matrix whit their square root ?

I need to replace every positive value from this matix whit their square root

A = [1 1 2 3 5 8; 0 2 4 6 8 10; -1 -3 -5 -7 -9 -11;2 4 8 16 32 64;13 21 34 55 89 144]; 

i tried this

A(A>0)=sqrt(A)

but it doesn't work and MATLAB show me this error

Unable to perform assignment because the left and right sides have a different number of elements.

Answer 1

[John D'Errico]

If you need to do it in one line, this will work:

A(A>0) = sqrt(A(A>0));

Or, you could do the test in advance, saving some CPU cycles.

So, why did your original idea not work? Because sqrt(A) has numel(A) elements in the result. However, A(A>0) does not have that many elements. So MATLAB tries to fit a square peg into a round hole, and then gives up. Unless you do as I suggested.

[David Gravano]

Thank you very much, it works