Re: Map onto a column
- To: mathgroup at smc.vnet.net
- Subject: [mg125502] Re: Map onto a column
- From: Thomas Dowling <thomasgdowling at gmail.com>
- Date: Thu, 15 Mar 2012 00:37:57 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <201203130802.DAA12753@smc.vnet.net>
Another possibility:
ReplacePart[#, 2 -> f@#[[2]]] & /@ a
giving
{{1, f[2], 3}, {4, f[5], 6}, {7, f[8], 9}}
Tom Dowling
On Tue, Mar 13, 2012 at 8:02 AM, Sly Pandemia <slypandemia 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?
>
>
- References:
- Map onto a column
- From: Sly Pandemia <slypandemia@gmail.com>
- Map onto a column