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

4 次查看（过去 30 天）
Emma Kuttler
Emma Kuttler 2022-3-22
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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回答（1 个）

Voss
Voss 2022-3-22
Ran in:
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
  2 个评论
Emma Kuttler
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
Voss 2022-3-24
编辑：Voss 2022-3-24
Ran in:
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

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