       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.)
>
>
>
>
>

```

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