# Is there a way to find number of blocks in a matrix?

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Omar B. on 15 Jun 2021
Commented: Omar B. on 15 Jun 2021
I have a matrix that has 5 blocks along the diagonal and two consecutive blocks overlap in one diagonal element.
How can I compute the number of blocks in MATLAB?
Joseph Cheng on 15 Jun 2021
can you explain what you mean by a block?

Stephen Cobeldick on 15 Jun 2021
Edited: Stephen Cobeldick on 15 Jun 2021
Assuming that the blocks do not contain zeros:
A = [1,2,0,0,0,0,0,0,0;3,4,5,6,0,0,0,0,0;0,7,8,9,0,0,0,0,0;0,1,2,3,4,5,0,0,0;0,0,0,1,2,3,0,0,0;0,0,0,1,2,3,4,5,0;0,0,0,0,0,1,2,3,0;0,0,0,0,0,1,2,3,4;0,0,0,0,0,0,0,1,2]
A = 9×9
1 2 0 0 0 0 0 0 0 3 4 5 6 0 0 0 0 0 0 7 8 9 0 0 0 0 0 0 1 2 3 4 5 0 0 0 0 0 0 1 2 3 0 0 0 0 0 0 1 2 3 4 5 0 0 0 0 0 0 1 2 3 0 0 0 0 0 0 1 2 3 4 0 0 0 0 0 0 0 1 2
[R,~] = find(diff(~A,1,1)>0);
N = 1+numel(unique(R))
N = 5
If the blocks can contain zeros, then you will probably need to use some pattern matching.
Omar B. on 15 Jun 2021
Thank you so much.