how to generate all possible combination from a sequence

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how to generate all possible combination from a n-dimensional vector without repetition of numbers.. i wanted combination of vec = 1:11;
eg:
vec = [1 2 3]
result = [
1 2 3;
1 3 2;
2 3 1;
2 1 3;
3 2 1;
3 1 2];
  1 Comment
Stephen23
Stephen23 on 28 May 2016
Edited: Stephen23 on 28 May 2016
Your question is erroneous: these are not the combinations of vec, but are actually the permutations.
The difference is very simple:
  • if the order does not matter: combinations.
  • if the order is important: permutations.
You should make a complaint to your high school that they did not teach these basic mathematical terms correctly. Ask for your money back!

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Accepted Answer

Stephen23
Stephen23 on 28 May 2016
>> perms(1:3)
ans =
3 2 1
3 1 2
2 3 1
2 1 3
1 2 3
1 3 2
  5 Comments
Stephen23
Stephen23 on 30 May 2016
Edited: Stephen23 on 30 May 2016
@Elysi Cochin: essentially you have two choices:
  1. buy more memory for your computer.
  2. change your algorithm.
As the other commenters have already told you, even though beginners often imagine that their computer has never-ending memory and processing capabilities, in practice it is very simple to define a few commands that far exceed any computer's abilities.
Your task (as the author of your algorithm) is to understand this and to get information on alternatives. One possibility is to use a permutation generator that generates each permutation at a time (not all at once). This will be slow, but it will avoid the memory problems. You will find several submissions on FEX that provide this functionality:
Ultimately however, you will just find that this takes too long, and you will then have to consider alternatives to your algorithm. Good luck!

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More Answers (1)

Jos (10584)
Jos (10584) on 30 May 2016

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