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MathGroup Archive 2006

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Re: Or in a Select question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67076] Re: Or in a Select question
  • From: "J Siehler" <jsiehler at gmail.com>
  • Date: Fri, 9 Jun 2006 01:06:36 -0400 (EDT)
  • References: <e68q6i$d0p$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

>  From here I would like to select all the elements whose sublists
> contain only different elements.  So my "logical" selection was:
> In[54]:=
> Select[pp,
>    #1[[1,1]] =!= #1[[1,2]] ||
>      #1[[2,1]] =!= #1[[2,
>        2]] & ]
> Out[54]=
> {{{a, a}, {a, b}},
>    {{a, b}, {a, c}},
>    {{a, c}, {b, a}},
>    {{b, a}, {b, b}},
>    {{b, b}, {b, c}},
>    {{b, c}, {c, a}},
>    {{c, a}, {c, b}},
>    {{c, b}, {c, c}}}

The criterion you've written is, return any element where at least one
pair contains two different elements.  So {{a,a},{a,b}} is selected
because of the {a,b}; {{b,b},{b,c}} is selected because of the {b,c},
stb.

Unless I badly misunderstood the question, you just want && instead of
|| : The first list should have distinct elements AND the second list
should have distinct elements.

In[24]:=
Select[pp,(#1[[1,1]]=!=#1[[1,2]])&&(#1[[2,1]]=!=#1[[2,2]])&]

Out[24]=
{{{a,b},{a,c}},{{a,c},{b,a}},{{b,c},{c,a}},{{c,a},{c,b}}}


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