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Re: Apply function to parts of a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86255] Re: Apply function to parts of a list
  • From: Peter Breitfeld <phbrf at t-online.de>
  • Date: Fri, 7 Mar 2008 02:26:14 -0500 (EST)
  • References: <fqo8pn$svq$1@smc.vnet.net>

guerom00 schrieb:
> Hi all,
>
> Very often, I find myself having datas to plot of this form :
>
> data={{x1,y1},{x2,y2},{x3,y3}...{xn,yn}}
>
> So, very conventional : a list of abscissa and ordinate. Now, let's say I want to multiply by 2 all my ascissa. Right now, I write :
>
> MapAt[2*#&,data,Table[{i,1},{i,1,Length[data]}]]
>
> It's OK but I isn't there another way to achieve this as I find this rather "involved" for such a simple thing ?
>
> Thanks in advance.
>

One possibility is

{2#[[1]],#[[2]]}&/@data

or with a rule:

data/.{x_,y_}->{2x,y}

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


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