How to select rows of matrix based on other matrix column?

Question

Emma Kuttler 2022-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/1678129-how-to-select-rows-of-matrix-based-on-other-matrix-column

编辑： Voss 2022-3-24

Hi, I have a single column matrix called "nodes" and a larger matrix with many columns called "arcs". If values from "nodes" appear in both of the first two columns of "arcs", I want to return that row from "arcs" and put it in a new matrix. If one or both of the values in the first two columns of "arcs" does not appear in "nodes", do not return that row.

For example, if these are the matrices nodes and arcs, I want to produce "arcssmall"

nodes = [1
         2
         4
         6
         9
         11]
arcs = [1 2 0 1 4
        1 3 9 8 7
        2 1 8 3 0.5
        4 11 9 0 0
        6 9  5 5 5 
        5 6  1 2 3
        9 1  0 0 0
        7 8  6 7 7]
arcssmall = [1 2 0 1 4
             2 1 8 3 0.5
             4 11 9 0 0
             6 9  5 5 5 
             9 1  0 0 0]

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Answer 1

Voss 2022-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/1678129-how-to-select-rows-of-matrix-based-on-other-matrix-column#answer_924524

在 MATLAB Online 中打开

nodes = [1
         2
         4
         6
         9
         11];
arcs = [1 2 0 1 4
        1 3 9 8 7
        2 1 8 3 0.5
        4 11 9 0 0
        6 9  5 5 5 
        5 6  1 2 3
        9 1  0 0 0
        7 8  6 7 7];
arcssmall = arcs(all(ismember(arcs(:,[1 2]),nodes),2),:)
arcssmall = 5×5
    1.0000    2.0000         0    1.0000    4.0000
    2.0000    1.0000    8.0000    3.0000    0.5000
    4.0000   11.0000    9.0000         0         0
    6.0000    9.0000    5.0000    5.0000    5.0000
    9.0000    1.0000         0         0         0

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Emma Kuttler 2022-3-24

Thanks! How would I change the script so that I was only checking in the first column of arcs to see if there was a match for a value in nodes?

Voss 2022-3-24

编辑：Voss 2022-3-24

在 MATLAB Online 中打开

nodes = [1
         2
         4
         6
         9
         11];
arcs = [1 2 0 1 4
        1 3 9 8 7
        2 1 8 3 0.5
        4 11 9 0 0
        6 9  5 5 5 
        5 6  1 2 3
        9 1  0 0 0
        7 8  6 7 7];
% arcssmall = arcs(all(ismember(arcs(:,[1 2]),nodes),2),:)
arcssmall = arcs(ismember(arcs(:,1),nodes),:) % change [1 2] to just 1, and no need to use all(__,2) in this case
arcssmall = 6×5
    1.0000    2.0000         0    1.0000    4.0000
    1.0000    3.0000    9.0000    8.0000    7.0000
    2.0000    1.0000    8.0000    3.0000    0.5000
    4.0000   11.0000    9.0000         0         0
    6.0000    9.0000    5.0000    5.0000    5.0000
    9.0000    1.0000         0         0         0