Shared entropy of audio files

So after trying a heavy cicle based function to calculate the joint entropy of two information sources, I found this useful MATLAB function accumarray

and tried the following code:

function e = jointEntropy(fonte1, fonte2)
    i = double(fonte1(:))+ 1; 
    j = double(fonte2(:)) + 1; 

    subs = [i j];
    f = accumarray(subs, ones(length(fonte1), 1));
    p = f / length(fonte1);
    freq = f ~= 0;
    prob = p(freq);
    e = -sum(prob.*log2(prob));
end

      

        
        
        
      

    

where fonte1

and fonte2

are sources of information, arrays 1xN

. This worked very well with examples where both sources only had positive integer values, but then I tried to use it with sound files (i.e. Arrays that ranged from -1 to 1) and it kept giving me an error. I tried adding 1 to each array (0 to 2), multiplying them by 100 and rounding the numbers to get non-negative integers, but it still doesn't work.

Any idea / alternative to this code would be appreciated.