Re: Help with Select[]
- To: mathgroup at smc.vnet.net
- Subject: [mg34675] Re: Help with Select[]
- From: Mars.bbs at bbs.dartmouth.edu (Momotalo)
- Date: Fri, 31 May 2002 04:27:32 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
transpose the sublist,then determine if they are all zeros:)
Select[setA, (Plus @@ Abs[Transpose[#][[2]]] == 0) &]
>>------- kc144_nospam wrote:
: Hello all,
: I've got data sets that resemble
: setA={
: {{x1,0},{x2,0}},
: {{x3,0},{x4,0}},
: {{x5,1},{x6,0}},
: {{x7,1},{x8,1}}
: };
: setB={
: {{x1,0},{x2,0},{x3,0}},
: {{x4,0},{x5,0},{x6,0}},
: {{x7,1},{x8,0},{x9,1}},
: {{x10,1},{x11,1},{x12,0}}
: };
: Each element of the set is a list of n (x,y) ordered pairs. So n=2 for the
: first set and n=3 for the second set. In general, n will differ between the
: data sets, but can be known. With each set, I want to select those elements
: whose sub-elements all have y=0. This is hard to explain in English, but
: easy to express in Mathematica:
: In: Select[setA,(#[[1,2]]==#[[2,2]]==0)&]
: Out: {{{x1,0},{x2,0}},{{x3,0},{x4,0}}}
: In: Select[setB,(#[[1,2]]==#[[2,2]]==#[[3,2]]==0)&]
: Out: {{{x1,0},{x2,0},{x3,0}},{{x4,0},{x5,0},{x6,0}}}
: First, I would like to know how to generate an arbitrary "selection
: function" f[n] so that
: In: Select[setC,f[8]]
: Out: {{{x1,0},...,{x8,0}},{{x9,0},...,{x16,0}},...}
: Is it possible to construct such an f? Or is there a better way of
: accomplishing this task? It seems that perhaps pattern matching might be of
: use, but I haven't gotten too far with it.
: Thanks in advance,
: Kevin Gross
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