Extract row elements corresponding to a particular column value and save as new matrix

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Sarah
Sarah 2013-3-14
I have a Mx4 matrix with the following format:
a1 b1 c d1
a2 b2 c d2
a3 b3 c d3
a4 b4 c1 d4
a5 b5 c1 d5
and what i want to do is create new matrices corresponding to the different c values in the third column renaming this matrix matc.
Any help would be really appreciated Sarah

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回答（2 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-3-14
编辑：Azzi Abdelmalek 2013-3-14
b=A(:,3)
b(b==c)=yourvalue
A(:,3)=b
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Sarah
Sarah 2013-3-14
the matrices are being created correctly with the original code, I only wish to now save each matrix that was created within the loop eg after the assignin('base',sprintf('mat%d',c(k)),A(idx,:)) line. I appreciate your help with this!
Azzi Abdelmalek
Azzi Abdelmalek 2013-3-14
编辑：Azzi Abdelmalek 2013-3-14
% Check this: for c=2.4 the variable will be mat2p4 instead of mat2.4
A= [ 2 3 4 6
4 8 7 9
5 2 7 1
4 2 2.4 3]
A=sortrows(A,3)
b=A(:,3);
c=unique(b);
for k=1:numel(c)
idx=find(b==c(k));
s=num2str(c(k))
s=strrep(s,'.','p')
assignin('base',['mat' s],A(idx,:))
end
Check the result
mat2p4
mat4
mat7

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Sarah
Sarah 2013-3-14
So the matrix is sorted according to the third column so
A1=[4 2 2 3
2 3 4 6
4 8 7 9
5 2 7 1];
the answers should be
mat2=[4 2 2 3];
mat4=[2 3 4 6];
mat7=[4 8 7 9
5 2 9 1];

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