查找矩阵中每一行的出现次数

Question

I have a matrix that sorts based on its rows. in example the matrix may be as follow

M=[
0   3
1   1
1   2
1   2
1   2
1   2
1   3
1   3
2   0
2   2
2   2
2   3
3   2
3   3
3   3
];

I want to find the count of each repetitive row in above matrix

[0  3] count is 1
[1  1] count is 1
[1  2] count is 4
[1  3] count is 2
[2  0] count is 1
[2  2] count is 2
[2  3] count is 1
[3  2] count is 1
[3  3] count is 2

Answer 1

One solution would be to retrieve unique() occurrences of rows and then accumulate its index:

[unM, ~, subs] = unique(M,'rows');
[unM accumarray(subs,1)]
ans =
     0     3     1
     1     1     1
     1     2     4
     1     3     2
     2     0     1
     2     2     2
     2     3     1
     3     2     1
     3     3     2