extract all rows of a matrix except 'r' (vector) rows
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Hi! I need to extract all rows of 'matrix' except 'r' rows.
matrix = [54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65];
r = [1; 2; 3; 4: 9];
The result is:
matrix_out = [58; 59; 60; 61; 63; 64; 65];
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Stephen23
2023-9-8
The most efficient approach:
matrix = [54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65];
r = [1; 2; 3; 4; 9];
matrix_out = matrix;
matrix_out(r) = []
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更多回答(2 个)
Dyuman Joshi
2023-9-8
编辑:Dyuman Joshi
2023-9-8
matrix = [54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65];
r = [1; 2; 3; 4; 9];
%Method 1
%remove directly
matrix(r,:)=[];
%or
%Method 2
%remove indirectly
idx = 1:size(matrix,1);
ix = setdiff(idx,r);
matrix = matrix(ix,:);
Note that Method 1 won't work when there is an index not in the range of the dimensions of the array matrix.
For such cases, use Method 2.
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MarKf
2023-9-8
mat = magic(8)
r_not = [1 3:5 8];
mat(r_not,:) = [] %use mat_o = mat; to keep the original mat;
There are some issues with your example:
matrix = [54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65];
r = [1:3, 6, 9]; %btw this did not work with those dimensions;
% also not the way you wanted with those indices (matrix_out just removed 1:3)
matrix_out = matrix;
matrix_out(r,:) = []
Since yours is a simple vector, matrix_out(r) = []; would have worked easily too
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