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Re: Distribute one list element over another

  • To: mathgroup at smc.vnet.net
  • Subject: [mg130483] Re: Distribute one list element over another
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Mon, 15 Apr 2013 02:28:38 -0400 (EDT)
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  • References: <20130414003835.166586A91@smc.vnet.net>

The following is an "extravagant" solution in that it first constructs more pairs than are actually needed and then throws away what's not needed.

  First@Outer[List, Most@#, Last@#] & /@ data


On Apr 13, 2013, at 8:38 PM, Timm Reinisch <timm.reinisch at sprechkultur.com> wrote:

>
> It's difficult to explain what I want to achieve and maybe if I could
> describe it better I  would have been able to google a solution.
>
> My problem deals with lists of lists of the form {a1, a2,  a3, {m1, m2,
> m3, m4}}
>
> e.g.
>
> data =
> {
> {a1, a2,  a3, {m1, m2, m3, m4}},
> {b1, b2,  b3, {n1, n2, n3, n4}},
> {c1, c2,  c3, {o1, o2, o3, o4}},
> {d1, d2,  d3, {p1, p2, p3, p4}},
> }
>
> I want is to go over the list and transform each of the sublists {a1,
> a2,  a3, {m1, m2, m3, m4}} into a list consisting of pairs {{a1, m1}, 
> {a1, m2}, {a1, m3}, {a1, m4}}
> so that for the list given above I get
>
> {
> {{a1, m1},  {a1, m2}, {a1, m3}, {a1, m4}},
> {{b1, n1},  {b1, n2}, {b1, n3}, {b1, n4}},
> {{c1, o1},  {c1, o2}, {c1, o3}, {c1, o4}},
> {{d1, p1},  {d1, p2}, {d1, p3}, {d1, p4}},
> }
>
> I think it could be possible to do this using two nested map operations
> /@, but I don't find out how to do so exactly, because I run into
> trouble with the scope of the #
>
> What I'm doing at the moment is that I use a module:
>
> verteilen[liste_] := Module[{},
>  {#[[1]], liste[[1]]} & /@ liste[[4]]
> ]
>
> and map it over the list I want to transform:
>
> verteilen[#] & /@ data
>
> I'm searching for a much mor elegant way to achive this transformation,
> any hints?
>
> Thanks and best regards
>
> Timm
>

---
Murray Eisenberg                                    murray at math.umass.edu
Mathematics & Statistics Dept.      
Lederle Graduate Research Tower            phone 413 549-1020 (H)
University of Massachusetts                               413 545-2838 (W)
710 North Pleasant Street                         fax   413 545-1801
Amherst, MA 01003-9305








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