Re: Map onto one column of a matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg95528] Re: Map onto one column of a matrix*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Wed, 21 Jan 2009 06:43:00 -0500 (EST)*Organization*: Uni Leipzig*References*: <gl49tb$g7v$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, data = {{a, b}, {c, d}}; MapAt[f, #, {-1}] & /@ data data /. {q_, r_?AtomQ} :> {q, f[r]} Regards Jens . 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 >