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Re: Position of element in a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg16382] Re: Position of element in a list
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Thu, 11 Mar 1999 02:16:50 -0500
  • References: <7bt665$ndn@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Roger Mason wrote in message <7bt665$ndn at smc.vnet.net>...
>Hi,
>
>I want to find the Position[] of negative elements in a list. The obvious
>methods do not work:
>
>Position[{-1, 3, -2, 1}, -_]
>
>and
>
>Position[{-1, 3, -2, 1}, -x_]
>
>return
>
>{}
>
>So how do I perform this apparently simple task?
>
>Thanks,
>
>Roger Mason
>
>

Roger,

Position[{-1, 3, -2, 1}, _?Negative]

{{1},{3}}

Allan

---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565





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