Duplicating rows in a matrix
显示 更早的评论
Hi there
I have a matrix that i need to make twice as long. i.e i need to double the length of columns. eg i need:
[0 1 0 0]
[0 2 0 0]
to become:
[0 1 0 0]
[0 1 0 0]
[0 2 0 0]
[0 2 0 0]
Thanks
1 个评论
Just use REPELEM: https://www.mathworks.com/help/matlab/ref/repelem.html
A = [0,1,0,0;0,2,0,0]
B = repelem(A,2,1)
采纳的回答
Star Strider
2019-1-23
编辑：Star Strider
2019-1-23
Try this:
M = [0 1 0 0
0 2 0 0];
M2 = repmat(M, 1, 2);
M2 = reshape(M2', [], 4)'
producing:
M2 =
0 1 0 0
0 1 0 0
0 2 0 0
0 2 0 0
You could combine both calculations into a one-line calcualtion if you want to.
EDIT —
Generally, for ‘N’ repitions, the code becomes:
N = 4; % Number Of Repititions
Mn = repmat(M, 1, N)
Mn = reshape(Mn', [], 2*N)'
producing:
Mn =
0 1 0 0
0 1 0 0
0 1 0 0
0 1 0 0
0 2 0 0
0 2 0 0
0 2 0 0
0 2 0 0
3 个评论
Matthew Allison
2022-1-3
elegant solution.
to make this a truly generic solution, the 2*N should be replaced by m*N, where m is the number of rows being duplicated. The 2 assumes that the original array has only 2 rows.
Star Strider
2022-1-3
编辑：Star Strider
2022-1-4
@Matthew Allison — Thank you!
@Stephen — Because I wanted to make it general enough to work with earlier versions as well.
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