Re: How do I use Select[list,condition]?

*To*: mathgroup at smc.vnet.net*Subject*: [mg4540] Re: How do I use Select[list,condition]?*From*: earhart at athena.mit.edu (Elizabeth J Earhart)*Date*: Wed, 7 Aug 1996 04:17:46 -0400*Organization*: Massachvsetts Institvte of Technology*Sender*: owner-wri-mathgroup at wolfram.com

In article <4thatm$j6e at dragonfly.wolfram.com>, Jason Welter <welter at texoma.com> wrote: >I have a list that looks like: > >data = {{1,1,a,4,5,6},{2,1,a,2,3,4},{3,1,a,7,8,9}, > {1,2,b,4,5,6},{2,2,b,2,3,4},{3,2,b,7,8,9}, > {1,3,c,4,5,6},{2,3,c,2,3,4},{3,3,c,7,8,9}} > >and I want to pick out the lists that have a 2 as the second element >of the list. I tried something like: > >data1 = Select[data,data[[#,2]]==2]; > >but this doesn't work. How do I do it? data1 = Select[data,(#[[2]]==2)&]; Don't forget the '&' sign to signify a pure function - that's my own most common Mathematica typo (just edging out typing '=' instead of '=='). The test is performed on each element of data, not on the list as a whole. You could also use some variant on data1 = Cases[data, ls_List /; ls[[2]]==2]; I use this form more often because the format is interchangeable with Count[] and Position[]. -Elizabeth ==== [MESSAGE SEPARATOR] ====