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Re: Apply or Map on some parts of lists - help

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115620] Re: Apply or Map on some parts of lists - help
  • From: Ray Koopman <koopman at sfu.ca>
  • Date: Sun, 16 Jan 2011 05:55:42 -0500 (EST)
  • References: <igrqdn$qot$1@smc.vnet.net>

On Jan 15, 1:46 am, dragec <culino... at gmail.com> wrote:
> Dear,
> I have
>
> List like:
>
> { {{TITLE1},{{x11,y11},{x12,y12},{x13,y13},{x14,y14}}},
>   {{TITLE1},{{x21,y21},{x22,y22},{x23,y23},{x24,y24}}},
>   {{TITLE1},{{x31,y31},{x32,y32},{x33,y33},{x34,y34}}}
>
> }
>
> So, I would like to apply some function (eg. #/3.6&) to all y's.
> Is there any elegant way to do this.
> I Know that you know how to do this. :)
>
> THX

Here are two more suggestions. The first is a compact version of the
second suggestion in my second post. It exemplifies the sort of code
that gives functional programming a bad name.

MapAt[MapAt[f,#,2]&/@#&,#,2]&/@data

This one ought to be a little easier to follow. It's just a single
MapAt, with an (awkwardly constructed) list of where the y's are.

MapAt[f,data,Cases[Position[data,_,{4},Heads->False],{_,2,_,2}]]


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