Create unique sets of 3 from a vector of IDs?
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
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