How can i write a matlab code for making 3 digits pairs from a given binary sequence. and to store that pairs in a array for further use

I have a binary string of 27 bits: 111000111000100000010101100. I want to write a matlab code to make pairs of 3 bits to the string length like 111 000 111 000 100 000 101 110. and save these pairs as new symbols in an array like a=[111 000 111 000 100 000 101 110] please help me. Thank you in advance

Answer 1

[John D'Errico]

Be willing to learn. Try out the ideas posed in a solution. For example, given a vector of bits b...

b = '111000111000100000010101100';

reshape(b,3,[])'
ans =
111
000
111
000
100
000
010
101
100

See that reshape does create a convenient matrix of bits, where each row here is one of the desired 3 bit strings. Note that very often simple matrices like this are the best way to store such an array, as matrices are so easy to work with.

IF you are going to insist on what is essentially a cell array of bit strings, then a direct mat2cell call is simplest.

mat2cell(b,1,repmat(3,1,numel(b)/3))
ans = 
 '111' '000' '111'    '000'    '100'    '000'    '010'    '101'    '100'

Again, you will find that the simple flat array was easier to work with though.

[Image Analyst]

nice compact solution if his strings are always 27 bytes long. To be a little more robust, and handle cases where the string might not be exactly a multiple of 3 (like mine does :-) ), you could do this:

b = '11100011100010000001010110045'; % Not multiple of 3 long
leftOverCharacters = mod(length(b), 3)
if leftOverCharacters ~= 0
  message = sprintf('Warning: length of b is %d, which is not a multiple of 3', length(b));
  uiwait(warndlg(message));
  % Code to "fix" it.
  b3a = b(1:end-leftOverCharacters)
  b3a = mat2cell(b3a,1,repmat(3,1, numel(b3a)/3))
  % Tack on left over characters
  b3 = {b3a{:}, b(end-leftOverCharacters+1:end)}
else
  b3 = mat2cell(b,1,repmat(3,1,numel(b)/3))
end

[anuj tomar]

thanks sir its really helpfull....

[anuj tomar]

sir after making pairs of 3 bits.....can i apply huffman coding on output b3 please help...

Answer 2

[Roger Stafford]

Consult the documentation for matlab's 'reshape' function at:

 http://www.mathworks.com/help/matlab/ref/reshape.html

[John D'Errico]

Anuj - Try thinking creatively. If b is a bit vector, thus

b = '111000111000100000010101100';

then what would this do?

reshape(b,3,[])'

Perhaps that might indeed have helped you. If you are unwilling to think creatively in this way about how to solve your problem, then what would mat2cell have done here?

Don't shut your mind to solutions as posed. Instead, see what you can learn from them!

Answer 3

[Image Analyst]

Try this. Creates a cell array with 3 character strings in each cell.

s = '111000111000100000010101100'
lastIndex = length(s);
% Extract out 3 at a time and stick into 
% one cell of a cell array.
cellIndex = 1;
for index = 1 : 3 : lastIndex
  index2 = min(lastIndex, index+2);
  sParts{cellIndex} = s(index:index2);
  cellIndex = cellIndex + 1;
end
% Display it 
celldisp(sParts);

In the command window:

s =
111000111000100000010101100
sParts{1} =
111
sParts{2} =
000
sParts{3} =
111
sParts{4} =
000
sParts{5} =
100
sParts{6} =
000
sParts{7} =
010
sParts{8} =
101
sParts{9} =
100