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MathGroup Archive 1998

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Re: Help please: Summing a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg13499] Re: [mg13480] Help please: Summing a list
  • From: Hugh Walker <hwalker at gvtc.com>
  • Date: Fri, 31 Jul 1998 04:33:17 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

Rob Peterson at robpetersonSPAMME at iname.com wrote

>I make a list of numbers, eg:
>
>P=Table[6,{x,0,110}]; (I have a more interesting list to use later if I
>get this working)
>
>Now I want to make another list PP in which each entry PP[[i]] is the
>sum of P's first i entries.  I try
>
>PP[[i]]:=Sum[P[[n]],{n,0,i}];
>
>At the definition, I get the following error: Part::"pspec":
>    "Part specification \!\(n\) is neither an integer nor a list of
>integers."
>
>I don't know how to make n an integer.  In the definition of Sum[], it
>seems n is an integer unless you add a forth parameter "di" in the
>specification list such as
>Sum[f, {i, imin, imax, di}]
>
>Can anyone help me to generate this second list?
>

Hello Rob:

Here is another way to set up the sum function that should work OK.

P=Table[ Random [],{x , 1, 110}] ;
PP[i_] := Apply [ Plus,Take[ P, i ] ]

Cheers!


Hugh Walker
Professsor Emeritus
University of Houston

Gnarly Oaks



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