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MathGroup Archive 2003

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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



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