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Re: Lists: how to?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110014] Re: Lists: how to?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 29 May 2010 04:43:42 -0400 (EDT)

subs3[numbr_Integer] :=
 Subsets[Range[numbr], {3}]

data = subs3[7];

Select[data, FreeQ[#, 1 | 4 | 5] &]

{{2, 3, 6}, {2, 3, 7}, {2, 6, 7}, 
   {3, 6, 7}}

Cases[data, _?(FreeQ[#, 1 | 4 | 5] &)]

{{2, 3, 6}, {2, 3, 7}, {2, 6, 7}, 
   {3, 6, 7}}


Bob Hanlon

---- "S. B. Gray" <stevebg at ROADRUNNER.COM> wrote: 

=============
Hello:

I have this line

subs3 = Subsets[Range[numbr], {3}] which for numbr=7 gives subs3=

{{1,2,3}, {1,2,4}, {1,2,5}, {1,2,6}, {1,2,7}, {1,3,4}, {1,3,5},
  {1,3,6}, {1,3,7}, {1,4,5}, {1,4,6}, {1,4,7}, {1,5,6}, {1,5,7},
  {1,6,7}, {2,3,4}, {2,3,5}, {2,3,6}, {2,3,7}, {2,4,5}, {2,4,6},
  {2,4,7}, {2,5,6}, {2,5,7}, {2,6,7}, {3,4,5}, {3,4,6}, {3,4,7},
  {3,5,6}, {3,5,7}, {3,6,7}, {4,5,6}, {4,5,7}, {4,6,7}, {5,6,7}}

Given one of these sublists, say {1,4,5}, I want a nice way to delete 
all members of the subs3 list which have 1,4, or 5 in any one of the 
three positions. The reduced list in this example would be
{{2,3,6}, {2,3,7}, {2,6,7}, {3,6,7}}.

The way I'm doing it runs DeleteCases nine times. Is there a better way?

Steve Gray




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