How to calculate the Hamming weight for a vector?

Question

I am trying to calculate the Hamming weight of a vector in Matlab.

function Hamming_weight (vet_dec)
Ham_Weight = sum(dec2bin(vet_dec) == '1')    
endfunction

The vector is:

Hamming_weight ([208    15   217   252   128    35    50   252   209   120    97   140   235   220    32   251])

However, this gives the following result, which is not what I want:

Ham_Weight =

   10   10    9    9    9    5    5    7

I would be very grateful if you could help me please.

Answer 1

You are summing over the wrong dimension!

sum(dec2bin(vet_dec) == '1',2).'
ans =
   3   4   5   6   1   3   3   6   4   4   3   3   6   5   1   7

dec2bin(vet_dec) creates a matrix like this:

11010000
00001111
11011001
11111100
10000000
00100011
00110010
11111100
11010001
01111000
01100001
10001100
11101011
11011100
00100000
11111011

As you can see, you're interested in the sum of each row, not each column. Use the second input argument to sum(x, 2), which specifies the dimension you want to sum along.

Note that this approach is horribly slow, as you can see from this question.

EDIT

For this to be a valid, and meaningful MATLAB function, you must change your function definition a bit.

function ham_weight = hamming_weight(vector)     % Return the variable ham_weight 

ham_weight = sum(dec2bin(vector) == '1', 2).';   % Don't transpose if 
                                                 % you want a column vector
end                                              % endfunction is not a MATLAB command.