Hello.
I have the following problem: I have a matrix A (3x3), and I want to add elements to this matrix and create table B with dimensions 6x6. More specifically, I want the new data to be the same as the original ones.
A=(1 2 3; 4 5 6; 7 8 9)
% A=(1 2 3
% 4 5 6
% 7 8 9)
B=(1 1 2 2 3 3; 4 4 5 5 6 6; 7 7 8 8 9 9)
% B=( 1 1 2 2 3 3
% 4 4 5 5 6 6
% 7 7 8 8 9 9)
That is, the first element of table A (1,1) is 1. Then, in positions (1,1) (1,2) of the new matrix (B) it must again be 1. In position A (1,2) it is 2, then in positions (1,3) and (1,4) of B to appear 2. Respectively with the other elements. How is this done? Your help is important.

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Ameer Hamza
Ameer Hamza 2020-12-30
编辑:Ameer Hamza 2020-12-30
Use repelem()
A = [1 2 3; 4 5 6; 7 8 9]
B = repelem(A, 1, 2)
Note: In MATLAB [ ] are used to create arrays.

6 个评论

One more question. If based on the data in matrix A I want to make an matrix C (6X6) that has the following elements:
A=(1 2 3; 4 5 6; 7 8 9)
% A=(1 2 3
% 4 5 6
% 7 8 9)
C=(1 1 2 -2 3 -3; 4 -4 5 -5 6 -6; 7 -7 8 -8 9 -9)
% C=( 1 -1 2 -2 3 -3
% 4 -4 5 -5 6 -6
% 7 -7 8 -8 9 -9)
How is this done?
Try this
A = [1 2 3; 4 5 6; 7 8 9]
B = repelem(A, 1, 2)
C = B.*repmat([1 -1], size(A))
A = [1 2 3; 4 5 6; 7 8 9]
A = 3×3
1 2 3 4 5 6 7 8 9
B = kron(A, [1 -1])
B = 3×6
1 -1 2 -2 3 -3 4 -4 5 -5 6 -6 7 -7 8 -8 9 -9
I tried the C = B.*repmat([1 -1], size(A)). But I have the following issue now. when I want to create the matrix D
% D=(1 1 -1 -1 2 2 -2 -2 3 3 -3 -3
% 4 4 -4 -4 5 5 -5 -5 6 6 -6 -6
% 7 7 -7 -7 8 8 -8 -8 9 9 -9 -9)
I use this: D = B.*repmat([1 -1], size(A)), but the following error occurs: "Matrix dimensions must agree".
In this case, try
A = [1 2 3; 4 5 6; 7 8 9]
B = repelem(A, 1, 4)
D = B.*repmat([1 1 -1 -1], size(A))
or as Steven mentioned,
A = [1 2 3; 4 5 6; 7 8 9]
D = kron(A, [1 1 -1 -1])
It works. Thank you very much!!!!

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