Re: Map onto a column
- To: mathgroup at smc.vnet.net
- Subject: [mg125478] Re: Map onto a column
- From: Dana DeLouis <dana01 at me.com>
- Date: Thu, 15 Mar 2012 00:29:35 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
> b = Map[MapAt[f,#,2]&,a]
> b = MapAt[f,a,{All,2}] (...error)
>
> Is there any way to do what I want with a single Map/MapAt function?
Hi. Just another option:
m = {{1,2,3},{4,5,6},{7,8,9}};
m[[All,2]] = f/@m[[All,2]];
// or
m[[All,2]] = Map[f, m[[All,2]]];
m
{{1,f[2],3},{4,f[5],6},{7,f[8],9}}
= = = = = = = = = =
HTH :>)
Dana DeLouis
Mac & Math 8
= = = = = = = = = =
On Mar 13, 4:04 am, Sly Pandemia <slypande... at gmail.com> wrote:
> 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?