how do I count the number of identical rows in a matrix?

Hello,

I'm trying understand how to apply the huffman coding function to a matrix of the type:

0  22
1  12
0  4
1  1

...etc

which is the result of run length encoding on a bi level image. I need to obtain a vector with all the possible characters, an another with the corresponding probabilities for the huffman coding function to accept.

more simply put, I'm trying to find a way to find all the identical rows in this matrix, divide it by the total number of rows, and write the result in a vector.

Thanks very much for your help, and let me know if I didn't follow the appropriate formatting rules or if this question has been covered before - a search did not give any results.

[Matt J]

Your example doesn't have any identical rows in it. Show an example that does and what the output should be.

Answer 1

[Kye Taylor]

Let the N-by-2 matrix you're working with be denoted A.

Then, you can get a vector of size M-by-2 containing the unique rows with the command

uRows = unique(A,'rows');

Compute your empirical probability of each unique row with the commands

a = mat2cell(uRows,ones(1,size(uRows,1)),2); % convert to cell for cellfun

% function handle that takes a 1x2 row vector as input 
% and returns the number of matching rows in A.
g = @(row)nnz(ismember(A,row,'rows')); 

% the probability
puRows = cellfun(g,a)/size(A,1);

[reetu hooda]

Thank you so much! exactly what I wanted.