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Re: Re: Recursion on a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28940] Re: [mg28908] Re: Recursion on a list
  • From: Richard Palmer <mapsinc at bellatlantic.net>
  • Date: Sat, 19 May 2001 22:27:57 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I think a form like x = FoldList[Times,1,1+Rest[r]] would be still more
efficient and get the job done.  It avoids a lot of interpretive function
evaluations.


-- 
Richard Palmer   
12 Garvey Road
Framingham, MA 01701
508 877-3862




on 5/18/01 1:13 AM, Stephen P Luttrell at luttrell at signal.dra.hmg.gb wrote:

> 
> "msc" <mscmsc at mediaone.net> wrote in message news:9e02kg$305 at smc.vnet.net...
>> Greetings,
>> 
>> I'm looking for an efficient method (i.e., with the use of an explicit
> loop)
>> for the following problem. I am working with large lists (several thousand
>> elements) of data. Denote one such list r. I would like to define a new
> list
>> x such that:
>> 
>> 
>> x[0] = 1.0
>> 
>> x[t] = x[t-1]*(1.0 + r[t])
>> 
>> Can anyone suggest an efficient way?
> 
> This does what you want:
> 
> FoldList[#1(1+#2)&,1,r]
> 
> where r is the list of r-values, which would have been {r[1],r[2],r[3],..}
> in your notation.
> 
> --
> Stephen P Luttrell
> DERA, Malvern, U.K.
> luttrell at signal.dera.gov.uk
> 
> 
> 



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