Re: Combinations
- To: mathgroup at smc.vnet.net
- Subject: [mg30797] Re: [mg30769] Combinations
- From: Tomas Garza <tgarza01 at prodigy.net.mx>
- Date: Wed, 19 Sep 2001 00:16:36 -0400 (EDT)
- References: <200109100043.UAA00680@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Perhaps you never got a reply because you are posing an odd problem. Obtaining the "Actual" permutations of a list of n objects may be more or less difficult, depending on the size of n. But the number of permutations is simply n! Why should you want a "function" to compute the factorial of n? Same goes for the combinations of n objects taken r at a time, which are obtained using KSubsets in DiscreteMath`Combinatorica`. Again, their number is simply n!/(r! (n - r)!). Or, maybe I didn't understand your problem. Tomas Garza Mexico City ----- Original Message ----- From: "Dana" <ng_only at hotmail.com> To: mathgroup at smc.vnet.net Subject: [mg30797] [mg30769] Combinations > Hello. I have Mathematica 4.1 > > In a Program like Excel, or a hand-held calculator, one can return the > number of combinations and permutations. > > However, I can not find an equivalent function in Mathematica. > For example, Permutations[ ] returns a long list of all the "Actual" > permutations. > I am looking for just the final number. > If there is one, could you include 'how' you found it. I have looked > everywhere. > I know DiscreteMath`Combinatorica` has some stuff in it, but the Help system > appears not to explain many of them. > > I can write a custom function, but I am curious to find out if this function > is built in to Mathematica. > > I hope the answer is not to take the Length[ ] of a rather long list. > > TIA. Dana > > (I posted this question a month ago, but it never showed up in the > newsgroup, or in the archives. > I hope I am not doing something wrong.) > > > > >
- References:
- Combinations
- From: "Dana" <ng_only@hotmail.com>
- Combinations