Split a matrix at specific row

Hello,

I have a 105x4 matrix and a vector [11 12 11 11 12 12 13 11 12] where the sum represent the row size of the matrix. I want to divide the matrix into several matrix, the first will start at row 1 to 11 and give a 11x4 matrix. The second will start a 12 to 24 and give a 12x4 matrix.. etc.. How can i do that? i'm a little bit lost

Thanks in advance for your help

Answer 1

[Jos (10584)]

Use mat2cell:

M = randi(20, 105,4) ;
V =  [11 12 11 11 12 12 13 11 12] ;
C = mat2cell(M, V , size(M,2)) ;

Answer 2

[Akira Agata]

Like this?

% Input matrix (A) and vector (h)
A = rand(105,4);
h = [11 12 11 11 12 12 13 11 12];

% Calculate start- and end-row index based on the given vector
endIdx = cumsum(h);
startIdx = [1 endIdx(1:end-1)+1];

% Separate the matrix
C = arrayfun(@(x,y) A(x:y,:),startIdx,endIdx,'UniformOutput',false);

The result looks like:

>> C
C =
1×9 cell array
{11×4 double}    {12×4 double}    {11×4 double}    {11×4 double}    {12×4 double}    {12×4 double}    {13×4 double}    {11×4 double}    {12×4 double}

[Jos (10584)]

Why so difficult? More than a decade ago, Matlab has created the function mat2cell to do exactly this ...

[Akira Agata]

Yes, mat2cell has just slipped my mind. Thanks!

Answer 3

[Alex Grimaud]

Thanks for the reply, the two solution works perfectly. But mat2cell is more simple !