replace non-zero values with random numbers - matlab

Question

I have a zero-one matrix in MATLAB as follows:
[0 0 0 1 1 1
0 1 1 0 0 0
1 0 0 0 0 1
1 1 1 0 0 0
0 0 0 1 0 1]
I want to define another matrix including rand values instead of indexes of above matrix by 1. For instance the desired new rand matrix should be:
[0 0 0 0.2 0.2 0.1
0 0.6 0.7 0 0 0
0.4 0 0 0 0 0.6
0.7 0.8 0.5 0 0 0
0 0 0 0.3 0 0.4]
I used a two nested loop for to find non-zero values from first matrix and replace the rand values instead of them in a new matrix.
Is there any function of matlab to do it automatically, without using two nested loop for?

Answer 1

You can do it as follows:
A = ...
[0 0 0 1 1 1;
0 1 1 0 0 0;
1 0 0 0 0 1;
1 1 1 0 0 0;
0 0 0 1 0 1];
B = rand(size(A));
A(logical(A)) = B(logical(A));
A =
0 0 0 0.1320 0.2348 0.1690
0 0.3377 0.3897 0 0 0
0.9027 0 0 0 0 0.7317
0.9448 0.3692 0.4039 0 0 0
0 0 0 0.0598 0 0.4509
(I just took the basic rand-function, adjust it, as you need it)

Answer 2

You can slightly improve thewaywewalk's answer by generating only as many random numbers as you need. As a bonus, this approach allows to do everything in one line:
A(logical(A)) = rand(1,nnz(A));

Answer 3

If you're trying to replace the ones in matrix A with random numbers then you don't need any looping at all.
Here's one method.
a = double(rand(5,5)>.5); % Your binary matrix should be type double.
n = sum(a(:)); % Count the 1's.
a(a>0) = rand(1,n); % Replace the ones with rands.

Answer 4

If 'l' is a matrix containing zeros and non-zeros. Consider the scenarios below answering this question :
Replace all the zeros in matrix with random numbers :
l(l==0) = randn(1,size(l(l==0),1));
Replace all the positive values with random numbers :
l(l>0) = randn(1,size(l(l>0),1));
Replace all the negative values with random numbers :
l(l<0) = randn(1,size(l(l<0),1));
Replace all the 'NaN' with random numbers.
l(isnan(l)) = randn(1,size(l(isnan(l)),1));