Re: Map onto one column of a matrix
- To: mathgroup at smc.vnet.net
- Subject: [mg95535] Re: Map onto one column of a matrix
- From: dh <dh at metrohm.com>
- Date: Wed, 21 Jan 2009 06:44:21 -0500 (EST)
- References: <gl49tb$g7v$1@smc.vnet.net>
Hi,
try:
data = {{a, b}, {c, d}};
data[[All, 2]] = f /@ data[[All, 2]] ;
data
hope this helps, Daniel
D. Grady wrote:
> Hi, suppose we've got a matrix
>
> data = {{a, b}, {c, d}};
>
> and we want to map a function onto just the second column, so we want
> to end up with
>
> {{a, f[b]}, {c, f[d]}}.
>
> The best way I've found to do this is with MapAt:
>
> MapAt[f, data, Table[{i, 2}, {i, Length@data}]]
>
> Is there a better way? I keep hoping there's some notation similar to
> what's used in Part that lets you refer to a whole column with All,
> like data[[All,2]]. Thanks!
>
> -Daniel
>