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

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Omar B. 2021-6-15

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https://ww2.mathworks.cn/matlabcentral/answers/856430-is-there-a-way-to-find-number-of-blocks-in-a-matrix

评论： Omar B. 2021-6-15

采纳的回答： Stephen23

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?

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Omar B. 2021-6-15

As an example:

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]

How can I compute the number of blocks in MATLAB?

Joseph Cheng 2021-6-15

can you explain what you mean by a block?

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Answer 1

Stephen23 2021-6-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/856430-is-there-a-way-to-find-number-of-blocks-in-a-matrix#answer_725370

编辑：Stephen23 2021-6-15

在 MATLAB Online 中打开

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.