Re: nth differences
- To: mathgroup at smc.vnet.net
- Subject: [mg39873] Re: nth differences
- From: Ed Pegg Jr <xeipon at ix.netcom.com>
- Date: Sun, 9 Mar 2003 05:29:40 -0500 (EST)
- References: <b4c9lo$nqg$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Zachary Turner wrote:
> Say I have a list of k integers and I want to produce a list containing the
> first differences? For example, given {1, 2, 5, 7, 8, 9} the first
> differences are {1, 3, 2, 1, 1}, and the second differences are {2, -1, -1,
> 0}, the third are {-3, 0, 1}, etc
>
Differences[A_List] := Drop[A, 1] - Drop[A, -1];
NestList[Differences[#] &, {1, 2, 5, 7, 8, 9}, 3]
{{1, 2, 5, 7, 8, 9}, {1, 3, 2, 1, 1}, {2, -1, -1, 0}, {-3, 0, 1}}
Differences[{1, 2, 5, 7, 8, 9}]
{1, 3, 2, 1, 1}
--Ed Pegg Jr