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Re: How to get sub-list elements at certain position in a long list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg123103] Re: How to get sub-list elements at certain position in a long list
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Wed, 23 Nov 2011 07:07:43 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

On 11/22/11 at 5:36 AM, hitphyopt at gmail.com (Gy Peng) wrote:

>{{{{2.5}, {3.8, 31}, {54.23, 46.263, 45.987}, *{-82.1476,** 5.17782,
>-205.36}*}, {{2.5}, {4.2, 30}, {233.835, 46.469,
>46.819}, *{93.8625, -13.9818, -198.778}*}}, {{{2.5}, {4.1,30},
>{139.845, 15.719, 155.87}, *{93.6633,**4.46398, -205.432}*}, {{2.5},
>{2.6, 32}, {113.381, 40.988,85.09}, *{90.1206, 16.9792,
>-205.314}*}}, {{{2.5}, {3.1,30}, {113.858, 34.709, 87.567},
>*{55.3298,**17.7214, -211.648}*}, {{2.5}, {2.7, 30}, {110.54,
>31.595,85.601}, *{-25.8558, 175.588, -121.105}*
>}}}

>How do I get each 4th sublist element in the last level? I mean, I
>want to get a list looks like: {*{-82.1476, **5.17782, -205.36},
>**{93.8625, -13.9818, -198.778},**{90.1206, 16.9792,
>-205.314},**{55.3298,**17.7214, -211.648},**{-25.8558, 175.588,
>-121.105}}* which only includes every 4th element in the last level.
>Do I describe my question clearly?

>Better not to use any "For", simple Map or Thread method are
>preferred.

Let data be the starting array you posted after cleaning out the
asterisk characters. Then the desired result can be obtained bu

In[21]:= Join @@ data[[All, All, -1]]

Out[21]= {{-82.1476, 5.17782, -205.36}, {93.8625, -13.9818, -198.778},
    {93.6633, 4.46398, -205.432}, {90.1206, 16.9792, -205.314},
    {55.3298, 17.7214, -211.648}, {-25.8558, 175.588, -121.105}}




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