How can I get a random 0-1 matrix whose elements sum is equal to a defined number?

Hello I am new in Matlab, I habe generated the following random 0-1 matrix:

>> C=randi([0,1],5,3)

C =

       1     0     1
       0     1     0
       0     0     1
       1     1     0
       0     1     1

And I want that the sum of all the elements i equal to one number, for example 12.

I will really appreciate your help.

Thank you in advance

Answer 1

[Walter Roberson]

In the general case, see http://www.mathworks.com/matlabcentral/fileexchange/9700-random-vectors-with-fixed-sum

However, in the specific case of random values that are all either 0 or 1, and you need a fixed sum S and it has to go into an M x N matrix (e.g., 5 x 3) then

samples = [ones(1,S), zeros(1,M*N-S)];
C = reshape( samples( randperm(length(samples)) ), M, N);