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MathGroup Archive 2012

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Map onto a column

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125412] Map onto a column
  • From: Sly Pandemia <slypandemia at gmail.com>
  • Date: Tue, 13 Mar 2012 03:02:42 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Is there a neat way to map a function onto a specific column in an
array?

For example if I have

a = {{1,2,3},{4,5,6},{7,8,9}}

and I want to map f onto the second element in each row. I would
normally use

b = Map[MapAt[f,#,2]&,a]

but this seems a bit awkward. I would expect to be able to use

b = MapAt[f,a,{All,2}]

but this appears to be illegal syntax.

Is there any way to do what I want with a single Map/MapAt function?



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