Re: Map onto a column

*To*: mathgroup at smc.vnet.net*Subject*: [mg125498] Re: Map onto a column*From*: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>*Date*: Thu, 15 Mar 2012 00:36:33 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

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? Try this: a={{1,2,3},{4,5,6},{7,8,9}} a//MatrixForm {{1,2,3},{4,5,6},{7,8,9}} (1 2 3 4 5 6 7 8 9) Map[f,Transpose[a][[2]]] {f[2],f[5],f[8]} Have fun. Alexei BOULBITCH, Dr., habil. IEE S.A. ZAE Weiergewan, 11, rue Edmond Reuter, L-5326 Contern, LUXEMBOURG Office phone : +352-2454-2566 Office fax: +352-2454-3566 mobile phone: +49 151 52 40 66 44 e-mail: alexei.boulbitch at iee.lu<mailto:alexei.boulbitch at iee.lu>