problems with matrix splitting

2016 8 22
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更新时间：2016 8 22
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0 个投票

Hello everyone, I want to split the matrix in such a way that when elements of 1st column are equal, the correspnding elements can be splitted into another matrix. For example, i have the following matrix.
A = [ 1 2; 1 3; 1 4; 2 1; 2 4].
i want to get the following 2 matrices as the resulting matrices.
a1 = [2;3;4] and a2= [1;4]
i have just started learning the looping in MATLAB, your coperation will be highly appreciated.

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Azzi Abdelmalek
Azzi Abdelmalek 2016-8-22
编辑：Azzi Abdelmalek 2016-8-22

0 个投票

A = [ 1 2; 1 3; 1 4; 2 1; 2 4]
[ii,jj,kk]=unique(A(:,1),'stable')
out=accumarray(kk,A(:,2),[],@(x){x})
celldisp(out)

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pradeep kumar
pradeep kumar 2016-8-22
Thanks Azzi. That was a great help indeed. but , please note that in my actual problem A is a huge matrix of order (100 X 2). Is there anyway to use the accumarray inside a loop ? kindly help me.
Azzi Abdelmalek
Azzi Abdelmalek 2016-8-22
编辑：Azzi Abdelmalek 2016-8-22
Relatively, 100x2 is not Huge. And how do you want to use the loop?
pradeep kumar
pradeep kumar 2016-8-22
编辑：pradeep kumar 2016-8-22
I have no idea . So i am asking, is there any way ?
Azzi Abdelmalek
Azzi Abdelmalek 2016-8-22
I mean your question is not clear, why do you need a for loop, when accumarray can do the job?

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Stephen23
Stephen23 2016-8-22

1 个投票

Use accumarray:
out = accumarray(A(:,1),A(:,2),[],@(v){v})

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pradeep kumar
pradeep kumar 2016-8-22
Thanks Stephen. That was a great help indeed. but , please note that in my actual problem A is a huge matrix of order (100 X 2). Is there anyway to use the accumarray inside a loop ? kindly help me.

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