how to delete certain columns and rows from matrix
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Antrea Plastira
on 5 Oct 2022
Commented: William Rose
on 5 Oct 2022
I have the matrix
M = [1000 -1000 0 0;
-1000 10000 0 -9000;
0 0 5000 -5000;
0 -9000 -5000 14000];
and I want to get the matrix when the 1st column and row and the 3rd column and row are gone, so that Mnew = [10000 -9000;
-9000 14000];
Any help?
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Accepted Answer
William Rose
on 5 Oct 2022
M = [1000 -1000 0 0;
-1000 10000 0 -9000;
0 0 5000 -5000;
0 -9000 -5000 14000];
Mnew=M([2,4],[2,4])
The line above keeps specifies the rows and columns to keep.
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More Answers (2)
Steven Lord
on 5 Oct 2022
Do you know which rows/columns you want to delete or which ones you want to keep? If to keep:
M = magic(4)
toKeep = [2 4];
A = M(toKeep, toKeep)
If to delete:
M = magic(4)
toDelete = [1 3];
M(toDelete, :) = []
M(:, toDelete) = []
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William Rose
on 5 Oct 2022
If you want to sepcify the rows and columns to delete:
M = [1000 -1000 0 0;
-1000 10000 0 -9000;
0 0 5000 -5000;
0 -9000 -5000 14000];
Mnew=M;
rows2delete=[1,3];
cols2delete=rows2delete;
Mnew(rows2delete,:)=[];
Mnew(:,cols2delete)=[]
Try it.
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