how to find specific columns using vectors

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babis 2014-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/132664-how-to-find-specific-columns-using-vectors

回答： MiguelMauricio 2014-6-6

I have a matrix U (n*m) and vectors v(1)-v(m) [not the same size]. I want for every vector to find in the respective row (for vector v1 is row 1) the columns that have the vector number(for v1 [1; 8; 12; 52; 68; 93; 150; 189;] it selects columns 1,8,12,52,68,93,150,189) and then finds the 5 values that are closest to zero and rerurns vector v'(1)-v'(m) that have the number of the respective column(for example: v'(1)=[1;12;52;68;189;])

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Answer 1

MiguelMauricio 2014-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/132664-how-to-find-specific-columns-using-vectors#answer_139642

在 MATLAB Online 中打开

I am not sure I understood it completely

newMatrix=zeros(5,m);
for i =1:m
    rowU=U(:,i);
    %If you meant the columns with the indexes appearing in the vector v(i)
    indexes=v(i);
    %If you meant the columns with the same values as in the vector v(i)
    indexes=v(i)==rowU; %But v(i) and rowU must have the same length
    elementsRow=rowU(indexes);
    sortedElements=sort(abs(elementsRow)); %Close to zero in absolute value
    newMatrix(:,i)=sortedElements(1:5);
end