Binary numbers into array

I have a string n of N numbers (like '21325231214523234322' ) and their respective Huffman code ( {'10' } {'01' } {'00' } {'110' } {'111' } )

I would like to create an array with all the stream bits (01 10 00 ...)

stream = zeros(1,N);
for i=1:N
    value = str2num(n(i));
    stream(i) = str2num(ret{3,value});
end

where ret is a cell array with values, probabilities and then the Huffman codes.

This is not working because the codes starting with 0 will be converted to numbers and the 0s are lost (01 -> 0 , 00 -> 0).

Moreover,

stream(i) = ret{3,value};

is also not working: Unable to perform assignment because the left and right sides have a different number of elements.

How can I create my array?

Answer 1

[Rosario Frontino]

Solved.

If anyone's curious:

bitStream = {};
for i=1:N
    value = str2num(n(i));
    bitStream(i) = ret(3,value);
end

[Voss]

This solution relies on the numbers being integers starting with 1, so that you can use them as indices.

What happens if your numbers are like this? (Hint: an error occurs)

n = '76870786769078789877';
ret = { ...
    '6'  '7'  '8'  '9'   '0'; ...
    0.5  0.3  0.1  0.05  0.05; ...
    '10' '01' '00' '110' '111'}

ret = 3×5 cell array
    {'6'     }    {'7'     }    {'8'     }    {'9'     }    {'0'     }
    {[0.5000]}    {[0.3000]}    {[0.1000]}    {[0.0500]}    {[0.0500]}
    {'10'    }    {'01'    }    {'00'    }    {'110'   }    {'111'   }

try
    bitStream = {};
    N = numel(n);
    for i=1:N
        value = str2num(n(i));
        bitStream(i) = ret(3,value);
    end
catch ME
    disp(ME.message);
end % error:

Index in position 2 exceeds array bounds. Index must not exceed 5.

No error occurs in this case with my answer:

[~,idx] = ismember(n,[ret{1,:}]);
bitStream = ret(3,idx)

bitStream = 1×20 cell array
    {'01'}    {'10'}    {'00'}    {'01'}    {'111'}    {'01'}    {'00'}    {'10'}    {'01'}    {'10'}    {'110'}    {'111'}    {'01'}    {'00'}    {'01'}    {'00'}    {'110'}    {'00'}    {'01'}    {'01'}

Answer 2

[Voss]

Depending on what exactly you're after, one of these two very similar ways may work:

n = '21325231214523234322';
ret = { ...
    '1'  '2'  '3'  '4'   '5'; ...
    0.5  0.3  0.1  0.05  0.05; ...
    '10' '01' '00' '110' '111'}

ret = 3×5 cell array
    {'1'     }    {'2'     }    {'3'     }    {'4'     }    {'5'     }
    {[0.5000]}    {[0.3000]}    {[0.1000]}    {[0.0500]}    {[0.0500]}
    {'10'    }    {'01'    }    {'00'    }    {'110'   }    {'111'   }

[~,idx] = ismember(n,[ret{1,:}]);

% 1) stream is a character array of '0's and '1's:
stream = [ret{3,idx}]

stream = '01100001111010010011011011101000100110000101'

% or, 2) stream is a cell array of codewords:
stream = ret(3,idx)

stream = 1×20 cell array
    {'01'}    {'10'}    {'00'}    {'01'}    {'111'}    {'01'}    {'00'}    {'10'}    {'01'}    {'10'}    {'110'}    {'111'}    {'01'}    {'00'}    {'01'}    {'00'}    {'110'}    {'00'}    {'01'}    {'01'}