select a portion of the matrix

Question

Alberto Acri 2023-8-5

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2005012-select-a-portion-of-the-matrix

回答： Star Strider 2023-8-5

matrix_C.mat

Hi! I have the matrix 'matrix_C'. How can I stop (in this case) at the fifth row, i.e. when column 2,3,4 have 0 and column 5 a number?

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Answer 1

Star Strider 2023-8-5

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https://ww2.mathworks.cn/matlabcentral/answers/2005012-select-a-portion-of-the-matrix#answer_1283697

在 MATLAB Online 中打开

matrix_C.mat

One approach —

LD = load('matrix_C.mat');
C = LD.C
C = 7×5
    81    43   134   120   297
    82    32    77    73   182
    83     0    50    45   116
    84     0     0    35    76
    85     0     0     0    60
    86     0     0     0    44
    87     0     0     0    41
idx = find(sum(C(:,[2 3 4])==0,2)==3, 1);
Result = C(1:idx,:)
Result = 5×5
    81    43   134   120   297
    82    32    77    73   182
    83     0    50    45   116
    84     0     0    35    76
    85     0     0     0    60

.

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Answer 2

the cyclist 2023-8-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2005012-select-a-portion-of-the-matrix#answer_1283692

在 MATLAB Online 中打开

matrix_C.mat

The following does what you asked for, for this matrix. The "rule" you specified was not perfectly clear to me, though, so this may not generalize to other matrices in the way you want.

load("matrix_C.mat","C")
C
C = 7×5
    81    43   134   120   297
    82    32    77    73   182
    83     0    50    45   116
    84     0     0    35    76
    85     0     0     0    60
    86     0     0     0    44
    87     0     0     0    41
indexToLastRow = find(all(C(:,2:4)==0 & C(:,5)~=0,2),1);
C(1:indexToLastRow,:)
ans = 5×5
    81    43   134   120   297
    82    32    77    73   182
    83     0    50    45   116
    84     0     0    35    76
    85     0     0     0    60