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Retrieving minimum values for parts of a matrix

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Isma_gp
Isma_gp 2016-5-17
编辑： Matt J 2016-5-17
Hi, I have a matrix containing different rows with values for several years. I need to retrieve the minimum value corresponding to each year. For example: A=[ 1958 2; 1958 3; 1959 4; 1959 5; 1959 6 ] The result matrix that I need would be: B=[ 1958 2; 1959 4 ]
Could you please help with this? Thanks

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Azzi Abdelmalek
Azzi Abdelmalek 2016-5-17
编辑：Azzi Abdelmalek 2016-5-17
A=[ 1958 2; 1958 3; 1959 4; 1959 5; 1959 6 ]
[ii,jj,kk]=unique(A(:,1))
out=[ii accumarray(kk,(1:numel(kk))',[],@(x) min(A(x,2)))]

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Matt J
Matt J 2016-5-17
编辑：Matt J 2016-5-17
[i,~,s]=find( accumarray(A(:,1), A(:,2),[],@min ) );
B=[i,s]
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Matt J
Matt J 2016-5-17
编辑：Matt J 2016-5-17
You can be a bit more memory-conservative by making modifications like this,
[i,j,s]=find( accumarray(A(:,1)-1949, A(:,2),[],@min ) );
B=[i+1949,s]

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