How could I cut a matrix into subgroups?

How could I cut a matrix into several small groups according to the 1st column, and I don't know how many subgroups I may get and the size of the subgroups are not the same(rows).

Say I have a matrix,

1 23 34

1 2 3

3 45 76

3 5 66

3 2 7

3 23 32

4 2 2

4 5 27

4 1 0 ....

And finally, I would like to get :

1 23 34

1 2 3

and

3 45 76

3 5 66

3 2 7

3 23 32

and

4 2 2

4 5 27

4 1 0

and ...

How could I do that? Thanks in advance!

Answer 1

[Sean de Wolski]

[sz] = histc(X(:,1),unique(X(:,1))); %X is your matrix
C = mat2cell(X,sz,size(X,2)) %each cell will contain one matrix

This is tuned to work assuming column one is sorted if it's not:

X = sortrows(X,1);

[Zoe]

Thank you so much!

Answer 2

[Matt Fig]

A = round(rand(10,4));
B = mat2cell(A,[2 3 4 1],[2 2])

[Zoe]

Thank you so much!