how to generate all possible combination from a sequence

Question

Elysi Cochin 2016-5-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/286178-how-to-generate-all-possible-combination-from-a-sequence

编辑： Stephen23 2016-5-30

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 = [
2 3;
3 2;
3 1;
1 3;
2 1;
1 2];

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Stephen23 2016-5-28

编辑：Stephen23 2016-5-28

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!

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stephen23 2016-5-28

3
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/286178-how-to-generate-all-possible-combination-from-a-sequence#answer_223679

在 MATLAB Online 中打开

>> perms(1:3)
ans =
   2     1
   1     2
   3     1
   1     3
   2     3
   3     2

5 个评论
显示 3更早的评论隐藏 3更早的评论

Elysi Cochin 2016-5-30

i tried A=perms(uint8(1:11)) still Out of memory

Stephen23 2016-5-30

编辑：Stephen23 2016-5-30

@Elysi Cochin: essentially you have two choices:

buy more memory for your computer.
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:

http://www.mathworks.com/matlabcentral/fileexchange/22692-nextperm

http://www.mathworks.com/matlabcentral/fileexchange/13101-recperms--recursive-permutations-

http://www.mathworks.com/matlabcentral/fileexchange/23067-oneperm

http://www.mathworks.com/matlabcentral/fileexchange/24459-next-combination-permutation

Ultimately however, you will just find that this takes too long, and you will then have to consider alternatives to your algorithm. Good luck!

请先登录，再进行评论。