splitting matrix based on a value in one column

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masih
masih 2017-6-17
评论： Stephen23 2021-2-22
Hi All,
I have a very large matrix part of which looks like this:
7 0
10 0
16 0
19 1
26 1
29 1
3 1
5 0
69 0
36 0
78 0
as you can see, the second column is either 0 or 1. I want to split this large matrix into sub matrices such that each sub matrix represent only the parts where the second column is 0. How do we do this? Thanks.

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Stephen23
Stephen23 2017-6-17
编辑：Stephen23 2017-6-17
Hard-coded indexing:
>> M = [7,0;10,0;16,0;19,1;26,1;29,1;3,1;5,0;69,0;36,0;78,0];
>> M(M(:,2)==0,:)
ans =
7 0
10 0
16 0
5 0
69 0
36 0
78 0
>> M(M(:,2)==1,:)
ans =
19 1
26 1
29 1
3 1
General solution:
>> [~,~,X] = unique(M(:,2));
>> C = accumarray(X,1:size(M,1),[],@(r){M(r,:)});
>> C{1}
ans =
7 0
10 0
16 0
36 0
69 0
78 0
5 0
>> C{2}
ans =
26 1
19 1
29 1
3 1
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Pol Medir
Pol Medir 2021-2-22
How would you do this if the sample of data was too large to input manually?

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更多回答（1 个）

123456
123456 2018-7-18
How could I do the same thing but divide cell array by strings from one row? Let's say, that the array looks like that:
t2 1 2
t2 2 3
t1 3 4
t2 4 5
t1 5 6
t1 6 7
I would like to recieve two arrays at the end:
1 2
2 3
4 5
and
3 4
5 6
6 7
  1 个评论
Stephen23
Stephen23 2018-7-19
There are several solutions. One way is to input the first column into unique, and use its third output with my answer.

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