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MathGroup Archive 2006

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Re: List manipulation question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67219] Re: List manipulation question
  • From: "Dana DeLouis" <ddelouis at bellsouth.net>
  • Date: Tue, 13 Jun 2006 01:07:05 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi.  Just another option would be to use Bob's excellent idea, and solve for
the padded variables.  Thus:

 

 dif[v_?VectorQ] := ListConvolve[

 {1/2, 0, -(1/2)}, v, {2, -2}, 

 {2*v[[-1]] - v[[-2]], 2*v[[1]] - v[[2]]}]

 

v = {3700, 3800, 3900, 3950, 4000, 

 4050, 4100, 4150, 4200, 4250, 4300, 

 4350, 4400, 4450, 4500, 4550, 4600, 

 4650}; 

 

Your desired results:

 

result = {100, 100, 75, 50, 50, 50, 50, 

 50, 50, 50, 50, 50, 50, 50, 50, 50, 

 50, 50}; 

 

dif[v] == result

 

True


-- 
HTH.  :>)

 

Dana DeLouis
Windows XP, Mathematica 5.2

 

"LectorZ" <lectorz at mail.ru> wrote in message
news:e6ge0k$nh3$1 at smc.vnet.net...

> 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 should 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
>


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