Re: Using "Sum" (i = 1 ... N) in a function definition

*To*: mathgroup at smc.vnet.net*Subject*: [mg49828] Re: Using "Sum" (i = 1 ... N) in a function definition*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Tue, 3 Aug 2004 01:11:00 -0400 (EDT)*Organization*: The University of Western Australia*Sender*: owner-wri-mathgroup at wolfram.com

wilhelm.rainer at gmx.net (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 ...? There really is no need to define a function MyFunc. Instead just use FoldList: Rest[FoldList[Plus,0,{3,2,4,5,6}]] Cheers, Paul -- Paul Abbott Phone: +61 8 9380 2734 School of Physics, M013 Fax: +61 8 9380 1014 The University of Western Australia (CRICOS Provider No 00126G) 35 Stirling Highway Crawley WA 6009 mailto:paul at physics.uwa.edu.au AUSTRALIA http://physics.uwa.edu.au/~paul