(Ask again)Show every combination of N-dim vector.

Hello, I asked it the day before yesterday but the code some expert told does not work well.

He wrote:

[C{1:N}]=ndgrid(0:2);
M=reshape(vertcat(C{:}),[],N);

However, it does show 3^N rows, but not every combination of N-dim vector of {0,1,2}. Is there another way to show all 3^N combinations and put it in a matrix?

Thank you so much!

[Oleg Komarov]

Please familiarize with the formatting capabilites on: http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Especially with the code section.

[Sean de Wolski]

How does this not work?

If I use N = 4; I get an 81x4 matrix of all possibilities. 3^N is 81.

etc. for all N.

Please elaborate on what doesn't work and please post this as a comment in your other question.

[Daniel Shub]

@Sean you can double check your solution with unique(M, 'rows'), and it appears answers are repeated.

[Sean de Wolski]

huh, your fullfact one is better anyway.

[C Zeng]

Yes, Sean, your code gives 3^N rows, but they have repeated one. Also I do not understand what does it mean? It seems that it is going to construct a grid in graphics, right? But I want all factorial combinations.

Answer 1

[Daniel Shub]

I will repeat the answer I gave to your original question

x = fullfact([3,3,3])-1

EDIT

For a general N

N = 3;
x = fullfact(repmat(3, N, 1))-1

[Oleg Komarov]

One remark: needs Stat Toolbox.

I will add the wiki: http://en.wikipedia.org/wiki/Design_of_experiments

Alternatively a very useful FEX submission: http://www.mathworks.com/matlabcentral/fileexchange/24325-combinator-combinations-and-permutations

@Daniel: thank you, always glad to learn somethign new!

[Daniel Shub]

@Oleg it is worth taking a look at the code of fullfact. Usually I can have a vague idea what a function is doing pretty quickly, in this case I have no idea.

[Oleg Komarov]

"Doesn't matter had s.."

Somehow the citation sounds legit.

[C Zeng]

Daniel, thank you! If the dimension is N, how can I change it to N-dim vector? Say fullfact([3,3,3...,3])-1?

[Daniel Shub]

Yes, or even better repmat(3, N, 1)

[C Zeng]

Thank you, Oleg, your links are awesome!

[C Zeng]

Daniel, I am confused here, your full factorial design works for my purpose. I am asking whether I can set the dimension N, so I do not need to input 3 N times. repmat(3, N, 1) does not give what I want here. Can you advise?

[Daniel Shub]

See my edit.

[C Zeng]

Oh, yes, or using combinator.m file:

combinator(3,N)-1

Thank you so much!

Answer 2

[Daniel Shub]

I think http://www.mathworks.com/matlabcentral/fileexchange/10064-allcomb might do it also.