R help - Dec 2008 - Create unique sets of 3 from a vector of IDs?

Dear all:

This is one of those "should be easy" problems that I'm having
great difficulty solving. I have a vector containing ID codes, and I need to
generate a 3-column matrix that contains all possible combinations of three.

For example, my ID vector looks like this:
A
B
C
D
E

I need to generate a matrix that looks like this:
A B C
A B D
A B E
A C B
A C D
A C E
A D B
A D C
A D E
.... and so on. (Yes, this could yield some very large matrices!) It's
totally fine, though less desirable, if the resulting matrix contains
combinations with "duplicates," e.g., A A A, A A B, or whatever.

Thoughts? I'm pretty much stumped here. Thanks in advance for any help you
can offer.

Best regards,

Brandon

On Tue, Dec 2, 2008 at 7:42 PM, philozine <philozine at yahoo.com>
wrote:
> Dear all:
>
> This is one of those "should be easy" problems that I'm
having great difficulty solving. I have a vector containing ID codes, and I need
to generate a 3-column matrix that contains all possible combinations of three.
>
> For example, my ID vector looks like this:
> A
> B
> C
> D
> E
>
> I need to generate a matrix that looks like this:
> A B C
> A B D
> A B E
> A C B
> A C D
> A C E
> A D B
> A D C
> A D E
Hi,

Does this do what you want?

expand.grid(letters[1:5], letters[1:5], letters[1:5])


D

> .... and so on. (Yes, this could yield some very large matrices!) It's
totally fine, though less desirable, if the resulting matrix contains
combinations with "duplicates," e.g., A A A, A A B, or whatever.
>
> Thoughts? I'm pretty much stumped here. Thanks in advance for any help
you can offer.
>
> Best regards,
>
> Brandon
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>