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Re: Intersection problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125977] Re: Intersection problem
  • From: Fred Simons <f.h.simons at tue.nl>
  • Date: Wed, 11 Apr 2012 18:16:20 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201204100627.CAA10654@smc.vnet.net>

Op 10-4-2012 8:27, Cisco Lane schreef:
> I need to select out the elements of the first list whose first elements are contained in the second list. For example
>
> first list: {{a,x},{b,y},{c,z}}
>
> second list: {b,c,d}
>
> result: {{b,y},{c,z}}
>
> Is there a quick way to do this? Intersection, maybe somehow?
>
>
I am not sure if this is quick, but it is short:

Pick[list1, list1[[All, 1]], Alternatives @@ list2]


Regards,

Fred Simons
Eindhoven University of Technology



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