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Date:         Sat, 17 Sep 2005 23:14:13 -0400
Reply-To:     Richard Ristow <wrristow@mindspring.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Richard Ristow <wrristow@mindspring.com>
Subject:      Re: all combinations possible
Comments: To: Arnaldo Ferrari Nasi <vs.arni@tiscalinet.it>
In-Reply-To:  <6.1.0.6.0.20050917223213.02632840@pop.tiscali.it>
Content-Type: text/plain; charset="us-ascii"; format=flowed

This doesn't answer the question, but perhaps will help clarify it.

At 04:40 PM 9/17/2005, Arnaldo Ferrari Nasi wrote:

>I have 8 or more alphanumeric figures, i.e. A B C D E E A F, I want >all the combinations possible between them. > >A B C D E E A F >B C D E E A F A >C D E E A F A B

It looks like you're looking for the *permutations*; that is, all possible orders for the symbols, including all symbols each time. It's worth saying this, because in this context, "combinations" is a technical term with a different meaning, and could confuse

>I think is simple... if you know how.

I don't know how simple it is. I think there are a number of standard algorithms, but the only one I can think of off the top of my head is a recursive algorithm -- the program calls itself -- and that's very awkward to simulate in SPSS.

It would occur to me to Google for "permutation algorithm". Or, if possible, to ask a computer science faculty member for an algorithm, or references.

You have some repeating elements, so it's not regular permutations, it's permutations with certain elements indistinguishable. I don't know how much that complicates the algorithms for enumerating them.


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