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Re: rules on vector sequence

  • To: mathgroup at smc.vnet.net
  • Subject: [mg98087] Re: [mg98018] rules on vector sequence
  • From: Filippo Miatto <sottosupremo at gmail.com>
  • Date: Sun, 29 Mar 2009 02:49:44 -0500 (EST)
  • References: <11367732.52414.1238245886953.JavaMail.hanlonr@127.0.0.1>

Thank you Bob, that is faster than what i did.
And if i'll need to tweak the rules now i know how it works!
Filippo


On Mar 28, 2009, at 2:11 PM, Bob Hanlon wrote:

> 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



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