get p(qm) matrix from mn matrix and pq indexing matrix

Question

Daniel Neubauer 2022-10-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1829063-get-p-q-m-matrix-from-m-n-matrix-and-p-q-indexing-matrix

评论： Davide Masiello 2022-10-17

采纳的回答： Davide Masiello

在 MATLAB Online 中打开

hey everyone,

is there an elegant way to get the following:

C=rand(8,n) %given
index=[...
    1 5 1 2 3 4
    2 6 2 3 4 1
    3 7 6 7 8 5
    4 8 5 6 7 8
    1 5 1 2 3 4];
X=[...
    C(1,1) C(5,1) C(1,1) ... ... C(4,1)     C(1,n) C(5,n) C(1,n) ... ... C(4,n)
    C(2,1) C(6,1) C(2,1) ... ... C(1,1)     C(2,n) C(6,n) C(2,n) ... ... C(1,n)
    C(3,1) C(7,1) C(6,1) ... ... C(5,1) ... C(3,n) C(7,n) C(6,n) ... ... C(5,n)
    C(4,1) C(8,1) C(5,1) ... ... C(8,1)     C(4,n) C(8,n) C(5,n) ... ... C(8,n)
    C(1,1) C(5,1) C(1,1) ... ... C(4,1)     C(1,n) C(5,n) C(1,n) ... ... C(4,n)
    ]

X=C(index,:)

gives the information but not arranged as desired. it is for plotting cubes by edge coordinates in 3d with patch command.

thanks for any help!

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Answer 1

Davide Masiello 2022-10-17

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1829063-get-p-q-m-matrix-from-m-n-matrix-and-p-q-indexing-matrix#answer_1077213

编辑：Davide Masiello 2022-10-17

在 MATLAB Online 中打开

Something like this?

n = 3;
C = rand(8,n)
C = 8×3
8036    0.1626    0.1875
8851    0.4522    0.1023
8075    0.3073    0.0316
3548    0.5842    0.8018
6769    0.1753    0.1741
8239    0.0872    0.1524
0985    0.8049    0.5961
6590    0.9066    0.9541
index=[...
5 1 2 3 4
6 2 3 4 1
7 6 7 8 5
8 5 6 7 8
5 1 2 3 4];
X = reshape(C(index(:),1:n),size(index,1),size(index,2)*n)
X = 5×18
8036    0.6769    0.8036    0.8851    0.8075    0.3548    0.1626    0.1753    0.1626    0.4522    0.3073    0.5842    0.1875    0.1741    0.1875    0.1023    0.0316    0.8018
8851    0.8239    0.8851    0.8075    0.3548    0.8036    0.4522    0.0872    0.4522    0.3073    0.5842    0.1626    0.1023    0.1524    0.1023    0.0316    0.8018    0.1875
8075    0.0985    0.8239    0.0985    0.6590    0.6769    0.3073    0.8049    0.0872    0.8049    0.9066    0.1753    0.0316    0.5961    0.1524    0.5961    0.9541    0.1741
3548    0.6590    0.6769    0.8239    0.0985    0.6590    0.5842    0.9066    0.1753    0.0872    0.8049    0.9066    0.8018    0.9541    0.1741    0.1524    0.5961    0.9541
8036    0.6769    0.8036    0.8851    0.8075    0.3548    0.1626    0.1753    0.1626    0.4522    0.3073    0.5842    0.1875    0.1741    0.1875    0.1023    0.0316    0.8018