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MathGroup Archive 2004

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Re: Counting Runs

  • To: mathgroup at
  • Subject: [mg51960] Re: Counting Runs
  • From: Peter Pein <petsie at>
  • Date: Fri, 5 Nov 2004 02:19:44 -0500 (EST)
  • References: <cmclmu$i99$>
  • Sender: owner-wri-mathgroup at

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
Please forgive me. First I had another way to solve your problem in 
mind. Of course it's sufficient to define

countruns[data_, items_] :=
   Count[Split[data], {x__} /; x == #] & /@ items

Peter Pein

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