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MathGroup Archive 2004

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Re: Counting Runs

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51917] Re: [mg51890] Counting Runs
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Fri, 5 Nov 2004 02:17:09 -0500 (EST)
  • References: <200411040650.BAA18131@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 4 Nov 2004, at 15:50, Gregory Lypny wrote:

> Looking for an elegant way to count runs to numbers in a series.
> Suppose I have a list of ones and negative ones such as
> 	v={1,1,1,-1,1,1,1,1,1,-1,-1,-1,-1,1}.
> I'd like to create a function that counts the number of runs of 1s and
> -1s, which in this case is 3 and 2.
>
> 	Greg
>
>

Here is one way:

v = {1, 1, 1, -1, 1, 1, 1, 1, 1, -1, -1, -1, -1, 1};


With[{u=Split[v]},{Count[u,{Repeated[1]}],Count[u,{Repeated[-1]}]}]

{3,2}



Andrzej Kozlowski
Chiba, Japan
http://www.akikoz.net/~andrzej/
http://www.mimuw.edu.pl/~akoz/


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