Re: Select from list
- To: mathgroup at smc.vnet.net
- Subject: [mg87778] Re: Select from list
- From: dh <dh at metrohm.ch>
- Date: Wed, 16 Apr 2008 22:32:19 -0400 (EDT)
- References: <fu4fjb$nhp$1@smc.vnet.net>
Hi Steve,
simply use Position:
Position[ptX,{___,2,___,3,___}|{___,3,___,2,___}]
hope this helps, Daniel
Steve Gray wrote:
> I have a list like this:
>
> ptX=
> {{1, 2, 3, 4}, {1, 2, 3, 5}, {1, 2, 4, 5}, {1, 3, 4, 5}, {2, 3, 4, 5}}
>
> and I want a list pointing to all the sublists above that contain both
> a 2 and a 3. In this example I would get {1,2,5}. The best solution I
> have, with more generality, is:
>
> va = 2;
> vb = 3;
> za = Map[Cases[#1, va]&, ptX] /. {} -> {0}
> zb = Map[Cases[#1, vb]&, ptX] /. {} -> {0}
> Flatten[Position[za*zb, {va*vb}]]
>
> which gives
>
> {{2}, {2}, {2}, {0}, {2}}
> {{3}, {3}, {0}, {3}, {3}}
> {1, 2, 5}.
>
> (This doesn't work if va or vb is zero. That's ok.)
> There's probably a better way. Anyone? Thank you.
>
> Steve Gray
>