Re: Apply a function to parts of a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg110311] Re: Apply a function to parts of a list*From*: "Carl K. Woll" <carlw at wolfram.com>*Date*: Sun, 13 Jun 2010 04:09:09 -0400 (EDT)

On 6/12/2010 5:32 AM, Rui wrote: > 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 > > With: list = {{a, 5}, {b,6}, {c,7}}; You can do: list[[All,2]] /= 2 and list will have all second elements cut in half. In[114]:= list Out[114]= {{a, 5/2}, {b, 3}, {c, 7/2}} Carl Woll Wolfram Research