how to break up a huge matrix at a specific different rows breakpoints into several smaller matrices

I have a huge matrix that I need to sort and break up into smaller matrices, now given that we know the indcies of the rows where we should split the matrix and we alrady have these indecies stored somewhere in another matrix how can we break the matrix effeciently at those specific breakpoints into several smaller matrices?

[Chunru]

You can access to submatrix with the index known, without breaking it down. Can you elabrate why you need to break it down?

[MA]

the submatrices then should be stored each one of them independently in an extrenal file.

[Chunru]

For the sake of saving space of the large matrix, try to directly access to the submatrix, instead of reproducing the submatrices, if it is possible.

[MA]

thank you for replying back. if the goal was only accessing the submatrix I would do what you siad. but each submatrix represent a set of data for a spicific interval of time. and as a matter of organizing data and labeling them, we need to extract those submatrices and get them labeled for future use and then store them inedependently in some way for future use. I hope you have an effecient way to do that.

Answer 1

[Walter Roberson]

In the case where the indices indicate the beginnings of the new blocks:

TheMatrix = randi(9, 15, 2)

TheMatrix = 15×2

1 4 6 5 3 8 9 4 4 2 8 6 9 5 7 2 5 6 4 5

split_indices = sort(1 + randperm(14,2))  %beginnings of blocks

split_indices = 1×2

3 6

blk = diff([1 reshape(split_indices, 1, []) size(TheMatrix,1)+1]);

splits = mat2cell(TheMatrix, blk, size(TheMatrix,2))

splits = 3×1 cell array
    { 2×2 double}
    { 3×2 double}
    {10×2 double}

celldisp(splits)

 
splits{1} =
 
     1     4
     6     5

 
 
splits{2} =
 
     3     8
     9     4
     4     2

 
 
splits{3} =
 
     8     6
     9     5
     7     2
     5     6
     4     5
     8     4
     6     4
     2     5
     5     7
     9     4

 

[MA]

thank you for the quick answer and your huge collaboration I really appreciate it . But I still don't understand how this way will result in sppliting my matrix at the specific breakpoints or rows I desire, may you please explain more about the the lines above...

[Walter Roberson]

In your actual code, make split_indices the indices of the starts of each new section. Do not include index 1 or the index of the end of the block, just the internal indices. Then use the assignment to blk and the assignment to splits .

[MA]

Thank you very much it worked perfectly, I really appreciate the help!!