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Re: "expanding a list"

• To: mathgroup at smc.vnet.net
• Subject: [mg57881] Re: [mg57860] "expanding a list"
• From: János <janos.lobb at yale.edu>
• Date: Sat, 11 Jun 2005 03:35:37 -0400 (EDT)
• References: <200506100629.CAA15653@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

On Jun 10, 2005, at 2:29 AM, Mark Coleman wrote:

> Greetings,
>
> I'd like to construct a list as follows. Say I have a list of reals
> {x1,x2,x3,...xn}, and another list of integers {r,s}. I'd like to
> make a new list
>
> {{x1,x1,x1,...},{x2,x2,x2....},{x3,x3,x3,...},....,{xn,xn,xn,...}},
> where the first sublist is of length r, and the remaining sublists
> are of length s.
>
>
> Thanks,
>
> -Mark
>
>
>

In[1]:=
realst = Table[Random[Real,
     {0, 1}], {i, 10}]
Out[1]=
{0.03511701775322186,
   0.705212355575097,
   0.6872307166505668,
   0.8832229225445591,
   0.4979794496000192,
   0.11640215667914437,
   0.7490677658059693,
   0.8352690475872514,
   0.09008175864152665,
   0.1772237316561382}

In[2]:=
intlst = {5, 3}
Out[2]=
{5, 3}

In[5]:=
lst = First[Last[
     Reap[i = 0; While[
        i++ < Length[realst],
        If[i == 1, Sow[
          Table[realst[[i]],
           {j, intlst[[1]]}]],
         Sow[Table[realst[[
           i]], {j, intlst[[
           2]]}]]]]]]]
Out[5]=
{{0.03511701775322186,
    0.03511701775322186,
    0.03511701775322186,
    0.03511701775322186,
    0.03511701775322186},
   {0.705212355575097,
    0.705212355575097,
    0.705212355575097},
   {0.6872307166505668,
    0.6872307166505668,
    0.6872307166505668},
   {0.8832229225445591,
    0.8832229225445591,
    0.8832229225445591},
   {0.4979794496000192,
    0.4979794496000192,
    0.4979794496000192},
   {0.11640215667914437,
    0.11640215667914437,
    0.11640215667914437},
   {0.7490677658059693,
    0.7490677658059693,
    0.7490677658059693},
   {0.8352690475872514,
    0.8352690475872514,
    0.8352690475872514},
   {0.09008175864152665,
    0.09008175864152665,
    0.09008175864152665},
   {0.1772237316561382,
    0.1772237316561382,
    0.1772237316561382}}

• References:
  • "expanding a list"
    • From: Mark Coleman <mark@markscoleman.com>