Generate array of sequence pairs without iteration

Question

Sabyrzhan Tasbolatov 2023-1-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1902620-generate-array-of-sequence-pairs-without-iteration

评论： Dyuman Joshi 2023-1-29

If I have M = 13; N = 8; and I need following result

[1 1; 1 2; 1 3; 1 4; 1 5; 1 6; 1 7; 1 8;...
    2 1; 2 2; 2 3; 2 4; 2 5; 2 6; 2 7; 2 8; 3 1; ... 13 7; 13 8]

is there any built-in MATLAB functions to achieve this without iteration? I've tried repmat but couldn't figure out how to get the exact result.

Working solution is:

    a = [];
    for m = 1:13
        for n = 1:8
            a = [a [m n]];
        end
    end

Thanks

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Stephen23 2023-1-29

在 MATLAB Online 中打开

The standard MATLAB approach is to use NDGRID or MESHGRID:

M = 13;
N = 8;
[x,y] = meshgrid(1:M,1:N);
a = [x(:),y(:)]
a = 104×2
     1     1
     1     2
     1     3
     1     4
     1     5
     1     6
     1     7
     1     8
     2     1
     2     2

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Answer 1

Dyuman Joshi 2023-1-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1902620-generate-array-of-sequence-pairs-without-iteration#answer_1158795

编辑：Dyuman Joshi 2023-1-29

在 MATLAB Online 中打开

A combination of repelem and repmat -

M=13;N=8;
%corresponding arrays
m=1:M;n=1:N;
out1=[repelem(m',N,1) repmat(n',M,1)]
out1 = 104×2
     1     1
     1     2
     1     3
     1     4
     1     5
     1     6
     1     7
     1     8
     2     1
     2     2
out1(end,:)
ans = 1×2
    13     8

There is a function - combvec, however, it is a part of a toolbox -

out2=rot90(combvec(n,m),-1)
out2 = 104×2
   1
   2
   3
   4
   5
   6
   7
   8
   1
   2
out2(end,:)
ans = 1×2
   8

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Sabyrzhan Tasbolatov 2023-1-29

Thanks, first out1 works for me, though it needed to be in 1D with 2D elements [1 1; 1 2; 1 3; ...]

Dyuman Joshi 2023-1-29

在 MATLAB Online 中打开

"in 1D with 2D elements [1 1; 1 2; 1 3; ...]"

Do you mean like this?

[1 1 1 2 1 3 .. 13 8]

If yes, then you have inserted the semi-colon incorrectly in both your statements, it should be a regular comma. The way to achieve that would be -

M=13;N=8;
out=reshape([repelem(1:M,1,N);repmat(1:N,1,M)],1,[])
out = 1×208
     1     1     1     2     1     3     1     4     1     5     1     6     1     7     1     8     2     1     2     2     2     3     2     4     2     5     2     6     2     7

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