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

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MA on 13 Sep 2021
Commented: MA on 13 Sep 2021
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?
MA on 13 Sep 2021
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.

Walter Roberson on 13 Sep 2021
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 on 13 Sep 2021
Thank you very much it worked perfectly, I really appreciate the help!!

R2021a

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