Re: Using "Sum" (i = 1 ... N) in a function definition
- To: mathgroup at smc.vnet.net
- Subject: [mg49709] Re: [mg49666] Using "Sum" (i = 1 ... N) in a function definition
- From: Murray Eisenberg <murray at math.umass.edu>
- Date: Thu, 29 Jul 2004 07:43:26 -0400 (EDT)
- Organization: Mathematics & Statistics, Univ. of Mass./Amherst
- References: <200407271100.HAA11129@smc.vnet.net>
- Reply-to: murray at math.umass.edu
- Sender: owner-wri-mathgroup at wolfram.com
MyFunc[i_] := Fold[Plus, 0, Take[MyData, i]]
Rainer wrote:
> I was trying to define a function using the Sum command in the
> following way (simplified example):
>
> MyData = {3,2,4,5,6};
> MyFunc[i_] = Sum[MyData[[j]],{j,1,i}];
>
> As you can see, the idea is to use the length of the list (i)
> as a variable in the function definition, such that
>
> MyFunc[1] = 3
> MyFunc[2] = 3 + 2 = 5
> MyFunc[3] = 3 + 2 + 4 = 9
>
> etc. Mathematica does not like the abobe statements, and prints the
> following error message:
>
> "Part specification K$394 is neither an integer nor a list of
> integers."
>
> Does anybody know how to define (correctly) such a function. Should be
> possible ...?
> Thanks
> Rainer
>
>
--
Murray Eisenberg murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2859 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305
- References:
- Using "Sum" (i = 1 ... N) in a function definition
- From: wilhelm.rainer@gmx.net (Rainer)
- Using "Sum" (i = 1 ... N) in a function definition