Re: rules on vector sequence
- To: mathgroup at smc.vnet.net
- Subject: [mg98086] Re: [mg98018] rules on vector sequence
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sun, 29 Mar 2009 02:49:32 -0500 (EST)
- Reply-to: hanlonr at cox.net
a = Range[-2, 2];
n = 4;
Select[Tuples[
Table[a, {n}]], (Total[#] ==
0) &&
((n - Count[#, 0] == 2) || (n - Count[#, 0] == 4)) &]
Bob Hanlon
On Sat, Mar 28, 2009 at 9:11 AM , Filippo Miatto wrote:
> Dear all,
> I need to generate all the vectors, of a given length N, that have
> these three properties:
>
> 1- the entries have to be among -2,-1,0,1,2
> 2- the sum of all the entries has to be 0
> 3- only two or four of the entries can be different from 0
>
> do you have any suggestions on how i can do that? i tried something
> but without success.. expecially i don't know how to implement the
> third rule..
> thank you in advance!
> Filippo