Re: DeleteCases
- To: mathgroup at smc.vnet.net
- Subject: [mg98176] Re: DeleteCases
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Wed, 1 Apr 2009 05:57:45 -0500 (EST)
On 3/31/09 at 4:19 AM, sottosupremo at gmail.com (Filippo Miatto) wrote: >Dear all, 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? Given you are treating {a,a,b,b} the same as {b,b,a,a} I assume it doesn't matter which is saved. That is sorting each to put them into a standard I assume is acceptable. So, In[1]:= data = {{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}}; In[2]:= Union[Sort /@ data] Out[2]= {{0, 0, 1, 1}, {0, 0, 2, 2}, {0, 0, 3, 3}, {1, 1, 2, 2}, {1, 1, 3, 3}, {2, 2, 3, 3}} does the trick. If the list has elements with a pattern different than {a,a,b,b} that you want to preserve ordered as they are then Union[data/.{a_,a_,b_,b_}:>Sort[{a,a,b,b}] should work. And if you need to preserve the order in which each sublist appears, use DeleteDuplicates instead of Union