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MathGroup Archive 1999

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Re: Manipulating a list of pairs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19720] Re: Manipulating a list of pairs
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Mon, 13 Sep 1999 02:40:54 -0400
  • References: <7reco3$46o@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hans Steffani <hans.steffani at e-technik.tu-chemnitz.de> wrote in message
news:7reco3$46o at smc.vnet.net...
>
> I have a list of pairs and manipulate it with things like
>
> lumpi[{f_, amp_}]:={f, Power[2 Pi f,2] U / amp}
> Map[ lumpi, thelist]
>
> is there an easier way without introducing "lumpi" to do this?
>
> Hans Friedrich Steffani
> --
> Hans Friedrich Steffani
> Institut fuer Elektrische Maschinen und Antriebe, TU Chemnitz
> mailto:hans.steffani at e-technik.tu-chemnitz.de
> http://www.tu-chemnitz.de/~hfst/
>

Hans,

Pure functions (anonymous functions) are useful for this sort of thing:

Two ways:

{#[[1]], Power[2 Pi #[[1]], 2] U/#[[2]]} & /@ thelist

{{1, 2*Pi^2*U}, {3, 9*Pi^2*U}}

{#1, Power[2 Pi #1, 2] U/#2} & @@@ thelist

{{1, 2*Pi^2*U}, {3, 9*Pi^2*U}}


A @@@ B   means   Apply[A, B, {1}] (new in version 4.0)


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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