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
>