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MathGroup Archive 2006

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Re: List manipulation question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67196] Re: List manipulation question
  • From: Peter Pein <petsie at dordos.net>
  • Date: Sun, 11 Jun 2006 23:08:04 -0400 (EDT)
  • References: <e6ge0k$nh3$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

LectorZ schrieb:
> Dear experts,
> 
> I need to calculate distances between the elements of the following
> list:
> 
> list={3700, 3800, 3900, 3950, 4000, 4050, 4100, 4150, 4200, 4250, 4300,
> 4350,
> 4400, 4450, 4500, 4550, 4600, 4650}
> 
> with the following logic:
> 
> a) If it is the first element, then take the simple difference to the
> next (i.e. 3800 - 3700)
> b) If it is the last element, then take the simple difference to the
> second last (i.e. 4650 -4600)
> c) the difference for all elements in between shoud be calculated as
> (next - last)/2 (i.e. (3900 - 3700)/2)
> 
> This list should come out as a result:
> 
> result={100,100,75,50,50,50,50,50,50,50,50,50,50,50,50,50,50,50}
> 
> Thanks a lot for your help
> 
> LZ
> 
try

diff=Flatten[{list[[2]]-list[[1]],(Drop[list,2]-Drop[list,-2])/2,list[[-1]]-list[[-2]]}]

or

diff2=Flatten[Insert[(Rest[list]-Most[list])[[{1,-1}]],(Drop[list,2]-Drop[list,-2])/2,2]];

Peter


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