Re: Match Pairs of Numbers
- To: mathgroup at smc.vnet.net
- Subject: [mg86900] Re: [mg86879] Match Pairs of Numbers
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Wed, 26 Mar 2008 04:47:27 -0500 (EST)
- Reply-to: hanlonr at cox.net
lst = {{1, 1}, {1, 2}, {1, 3}, {1, 4}, {2, 2}, {3, 1}, {3, 2}, {3, 3}, {4, 1}, {4, 4}}; Select[lst, MemberQ[DeleteCases[lst, #], Reverse[#]] &] {{1, 3}, {1, 4}, {3, 1}, {4, 1}} Cases[lst, _?(MemberQ[DeleteCases[lst, #], Reverse[#]] &)] {{1, 3}, {1, 4}, {3, 1}, {4, 1}} DeleteCases[lst, _?(FreeQ[DeleteCases[lst, #], Reverse[#]] &)] {{1, 3}, {1, 4}, {3, 1}, {4, 1}} Pick[lst, MemberQ[DeleteCases[lst, #], Reverse[#]] & /@ lst] {{1, 3}, {1, 4}, {3, 1}, {4, 1}} Bob Hanlon ---- Andrew Beveridge <acbev at lanl.gov> wrote: > Any help would be appreciated. > > I am using Mathematica 5.2 & 6.0 > > I am having trouble finding the correct form of Pattern Matching for > pairs of Numbers. I do not know whether to use Select, Cases, Pick, > etc. I am also unsure how to set the pattern matching argument. > > Assume I have the list > > lst = {{1,1}, {1,2}, {1,3}, {1,4}, {2,2}, {3,1}, {3,2}, {3,3}, {4,1}, {4,4}} > > > I would like to match/select pairs that have the same set of numbers > only reversed, that is, the selection would find > > {{1,3}, {3,1}, {1,4}, {4,1} } > > Thanks for your help > > > Andrew C Beveridge > MS M888 > Los Alamos National Laboratory > Los Alamos, NM 87545 > > 505-665-2092 > e-mail: acbev at lanl.gov > >