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MathGroup Archive 2003

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Re: nth differences

  • To: mathgroup at smc.vnet.net
  • Subject: [mg39900] Re: nth differences
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 11 Mar 2003 02:36:10 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <b4c9lo$nqg$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

NthDifference[lst_List, n_Integer] := 
  Nest[Drop[# - RotateRight[#], 1] &, lst, n]

and

lst = {1, 2, 5, 7, 8, 9};

Table[NthDifference[lst, i], {i, 1, 3}]

gives

{{1, 3, 2, 1, 1}, {2, -1, -1, 0}, {-3, 0, 1}}

Regards
  Jens


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


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