Re: DeleteCases

*To*: mathgroup at smc.vnet.net*Subject*: [mg98171] Re: DeleteCases*From*: Pillsy <pillsbury at gmail.com>*Date*: Wed, 1 Apr 2009 05:56:48 -0500 (EST)*References*: <gqsn69$3qp$1@smc.vnet.net>

On Mar 31, 5:19 am, Filippo Miatto <sottosupr... at gmail.com> wrote: > Given this example list: > {{0, 0, 1, 1}, {0, 0, 2, 2}, {0, 0, 3, 3}, {1, 1, 0, 0}, {1, 1, 2, 2}, = > {1, 1, 3, 3}, {2, 2, 0, 0}, {2, 2, 1, 1}, {2, 2, 3, 3}, {3, 3, 0, 0}, > {3, 3, 1, 1}, {3, 3, 2, 2}} > I need the elements {a,a,b,b} and {b,b,a,a} to be the same, i.e. i > want to delete one of the two occurrences from the list. (or all but > one if the condition is more complicated, say {a,b,c,d} and {b,a,c,d} > or {a,b,c,d} and {a,b,d,c}) > How can i do that? Can i use DeleteCases? if so, what conditional > should I use to compare different elements in the list? Here's one way of doing it, which depends on the function DeleteDuplicates[] from Mathematica 7. If you don't have Mathematica 7, things get a little trickier, I'm afraid, though if you at least have 6, you can fake it by defining, DeleteDuplicates[list_, test_] := First /@ Tally[list, test] Then you just need to make the test treat both its arguments as the same if they have the same elements in any order, which you can do with Sort[], like so: deleteOrderlessDuplicates[list_] := DeleteDuplicates[list, Sort[#1] === Sort[#2] & ] Cheers, Pillsy