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MathGroup Archive 2005

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Re: Simple task with Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63050] Re: Simple task with Mathematica
  • From: Peter Pein <petsie at dordos.net>
  • Date: Sun, 11 Dec 2005 22:25:24 -0500 (EST)
  • References: <dngvba$nd1$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Lea Rebanks schrieb:
> Dear Sir / Madame,
> 
> I am currently learning how to use Mathematica at college with a view to
> purchasing the program.
> 
> Having spent a week studying the documentation / Book etc of version 4 I
> am struggling to do even the most simple tasks. I have looked at other
> Math programs, but I am really impressed with the numerical precision &
> scope of Mathematica. Below is an example of a really easy task which I
> can do in a second in Excel, however I am stuck with Mathematica 4.
> Please show me the correct code to do in Mathematica. Many thanks for
> your attention.
> 
> Question:-
> 
> Given the two columns below; I am trying to take the first column (A)
> created as a list & iterate it by starting with 5 to finish with the
> second column using the function A(1) = (6.5*2)-5 (starting value from
> the second column) = 8. 
> 
> Then, for A(2) = (9.5*2)-8 =11 etc, etc giving the second column.
> Function A(x) = x*2.
> 
> (A)rea
> 
> 5
> 
> 
> 6.5
> 
> 8
> 
> 
> 9.5
> 
> 11
> 
> 
> 8.5
> 
> 6
> 
> 
> 4.5
> 
> 3
> 
> 
> 9
> 
> 15
> 
> 
> 12.5
> 
> 10
> 
> 
> 12.5
> 
> 15
> 
> 
> 17.5
> 
> 20
> 
> 
> 18.5
> 
> 17
> 
> 
> 11
> 
> 5
> 
>  
> 
> I have tried indexing with x = Range[11] & using A[[x]]-B[[x-1]]. Sorry,
> but I am really confused.
> 
>  
> 
> Many thanks for any help you can offer.
> 
>  
> 
> Best regards,
> 
>  
> 
> Lea Rebanks.
> 
Hi Lea,

if I understand you correctly, you want:

a={6.5,9.5,8.5,4.5,9,12.5,12.5,17.5,18.5,11};

FoldList[2*#2-#1&,5,a]
--> {5,8.,11.,6.,3.,15.,10.,15.,20.,17.,5.}

Peter


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