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Re: Select only certain sublists matching criteria

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110999] Re: Select only certain sublists matching criteria
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Fri, 16 Jul 2010 05:18:08 -0400 (EDT)
  • References: <i1mc7n$8u2$1@smc.vnet.net>

Chris Poole wrote:

> I have a list like this:
> {{0, -4, 2.283}, {0.5, -4, 2.282}, {1, -4, 2.280}, {1.5, -4, 
>   2.276}, {2, -4, 2.271}, {2.5, -4, 2.264}, {3, -4, 2.255}, {3.5, -4, 
>   2.242}}
>
> I want to look at each list of 3 numbers, and keep only the lists where the third item in each list fits some criteria.
>
> I can do something like this:
> Select[{2, 15, 1, 16, 17}, Abs[3 - #] < 3 &]
>
> But it only works for flat lists. 
>
> For example, I want only the lists where the third item is around 2.25 +- 0.001. Something like that.
>
> I can work out how to get Select to operate on the 3rd item of each sublist, but not how to then keep that entire list.
>
> If anyone has any ideas, they are much appreciated.
>

You may use (list is your List)

Select[list,Abs[#[[3]]-2.25]<0.01&]

Out={{3, -4, 2.255}, {3.5, -4, 2.242}}

-- 
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de


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