how to delete certain columns and rows from matrix

M = [1000       -1000           0           0;
    -1000       10000           0       -9000;
    0           0        5000       -5000;
    0       -9000       -5000       14000];
Mnew=M([2,4],[2,4])
Mnew = 2×2
       10000       -9000
       -9000       14000

The line above keeps specifies the rows and columns to keep.

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Antrea Plastira 2022-10-5

thank you!!

William Rose 2022-10-5

@Antrea Plastira, you're welcome.

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Answer 2

Steven Lord 2022-10-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1818265-how-to-delete-certain-columns-and-rows-from-matrix#answer_1067435

在 MATLAB Online 中打开

Do you know which rows/columns you want to delete or which ones you want to keep? If to keep:

M = magic(4)
M = 4×4
    16     2     3    13
     5    11    10     8
     9     7     6    12
     4    14    15     1
toKeep = [2 4];
A = M(toKeep, toKeep)
A = 2×2
    11     8
    14     1

If to delete:

M = magic(4)
M = 4×4
    16     2     3    13
     5    11    10     8
     9     7     6    12
     4    14    15     1
toDelete = [1 3];
M(toDelete, :) = []
M = 2×4
     5    11    10     8
     4    14    15     1
M(:, toDelete) = []
M = 2×2
    11     8
    14     1

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Answer 3

William Rose 2022-10-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1818265-how-to-delete-certain-columns-and-rows-from-matrix#answer_1067440

在 MATLAB Online 中打开

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)=[]
Mnew = 2×2
       10000       -9000
       -9000       14000