Generate combinations with scaleable code
2 views (last 30 days)
Show older comments
Howard Wilton
on 29 Dec 2022
Commented: Howard Wilton
on 29 Dec 2022
I have a tight piece of code which generates a 16x4 matrix which essentially is 16 vectors with 4 elements each and i want all the combinations where the vector elements are -1 or 1
[a1,a2,a3,a4] = ndgrid([1 -1],[1 -1],[1 -1],[1 -1]);
a_all_combos = [a1(:),a2(:),a3(:),a4(:)]
clear a1 a2 a3 a4
The code yields the following output:
1 1 1 1
-1 1 1 1
1 -1 1 1
-1 -1 1 1
1 1 -1 1
-1 1 -1 1
1 -1 -1 1
-1 -1 -1 1
1 1 1 -1
-1 1 1 -1
1 -1 1 -1
-1 -1 1 -1
1 1 -1 -1
-1 1 -1 -1
1 -1 -1 -1
-1 -1 -1 -1
However, this code does not scale-up nicely if I want nine-element vectors, yielding a
x9 matrix.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1246477/image.png)
Would welcome any suggestions on how to do this concisely.
0 Comments
Accepted Answer
the cyclist
on 29 Dec 2022
There happens to be a quite obfuscated way to do this:
n = 9;
a_all_combos = 2*(dec2bin(0:2^n-1) - '0') - 1
More Answers (0)
See Also
Categories
Find more on Matrices and Arrays in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!