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MathGroup Archive 2010

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Apply a function to parts of a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110299] Apply a function to parts of a list
  • From: Rui <rui.rojo at gmail.com>
  • Date: Sat, 12 Jun 2010 05:32:38 -0400 (EDT)

I have always done very ugly code when trying to do something
seemingly simple and basic such as applying a function to subparts of a list.
Simple example, I want to divide by 2 all the second elements of a
list
{{a, 5}, {b, 6}, ...}   -->  {{a, 5/2}, ...}

My ideas:
Transpose -> MapAt/Map -> Transpose
Build the sublist with Part and then rebuild it
Use Map and a function like #[[All, 2]] and then rebuild it.

I don't like any solution. I wanted to know if there's anything simple
that I'm overseing

Thanks guys


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