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MathGroup Archive 2001

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Re: Q: Extract Elements from a List?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28987] Re: [mg28968] Q: Extract Elements from a List?
  • From: Al Kaufman <nutronstar at rickadee.net>
  • Date: Thu, 24 May 2001 04:07:04 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

>hi!
>
>probably a very easy question, but i couldn't find an answer in the
>mathematica-book:
>
>i need to extract elements from a list, starting th element number x and
>than taking every yth element, eg:
>
>with
>
>lst={a,b,c,d,e,f,g,h,i,j}
>start=3;
>step=2;
>
>i'd like to get the list
>
>{c,e,g,i}.
>
>how can i do this in the easiest way?
>
>regards, robert


The solution is straight forward.  Use the Part function as the selector:

In[1]:=
lst = {a, b, c, d, e, f, g, h, i, j};
start = 3;
step = 2;
xtr = Part[lst,Table[p,{p,start,Length[lst],step}]];

In[2]:=
xtr

Out[2]:=
{c,e,g,i}

Good luck
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