RE: Sort on vector component

*To*: mathgroup at smc.vnet.net*Subject*: [mg122019] RE: [mg122006] Sort on vector component*From*: Richard Hofler <rhofler at bus.ucf.edu>*Date*: Sun, 9 Oct 2011 03:52:34 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201110080936.FAA21131@smc.vnet.net>

Hello, The answer that I believe you are looking for is given in the 3rd Basic Example in the Sort documentation: u={{2,12,7,21},{2,48,47,97},{4,42,41,87},{6,8,1,15},{6,12,9,27}}; Sort[u] (* sort on 1st element in each sublist *) Sort[u,#1[[2]]<#2[[2]]&] (* sort on 2nd element in each sublist *) Sort[u,#1[[3]]<#2[[3]]&] (* etc. *) Sort[u,#1[[4]]<#2[[4]]&] {{2,12,7,21},{2,48,47,97},{4,42,41,87},{6,8,1,15},{6,12,9,27}} {{6,8,1,15},{6,12,9,27},{2,12,7,21},{4,42,41,87},{2,48,47,97}} {{6,8,1,15},{2,12,7,21},{6,12,9,27},{4,42,41,87},{2,48,47,97}} {{6,8,1,15},{2,12,7,21},{6,12,9,27},{4,42,41,87},{2,48,47,97}} Richard Hofler ________________________________________ From: Dr. Wolfgang Hintze [weh at snafu.de] Sent: Saturday, October 08, 2011 5:36 AM To: mathgroup at smc.vnet.net Subject: [mg122019] [mg122006] Sort on vector component Given a list u = {{2, 12, 7, 21}, {2, 48, 47, 97}, {4, 42, 41, 87}, {6, 8, 1, 15}, {6, 12, 9, 27}} How can I sort it with respect to a given index position i=(1, ..., 4)? For i=1 it is simply Sort, for the last one I could use In[75]:= Reverse /@ Sort[Reverse /@ u] Out[75]= {{6, 8, 1, 15}, {2, 12, 7, 21}, {6, 12, 9, 27}, {4, 42, 41, 87}, {2, 48, 47, 97}} I don't want to go in the details of defining lexicographical order but just obtain a sorting as described above. Any ideas? Thanks in advance. Wolfgang

**References**:**Sort on vector component***From:*"Dr. Wolfgang Hintze" <weh@snafu.de>