Please, help me vectorize this code

[Pablo Fernández Bustamante]

Hi,

I want the elements of a matrix M_ to be equal to those of an original 
matrix M but only if they satisfy a certain condition, otherwise write a 
zero.

The following lines of code work as expected but I want to avoid the
loop if it is possible.

>> M = floor(rand(5, 4)*10);
>> [r, c] = find(M > 4);
>> M_ = zeros(5, 4);
>> for n = 1:length(r)
M_(r(n), c(n)) = M(r(n), c(n));
endfor

I have tried

M_ = M(find(M>4));

but that returns a column vector of the elements which satisfy the 
condition.

Thanks in advance,

Pablo