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

*To*: mathgroup at smc.vnet.net*Subject*: [mg49724] Re: Using "Sum" (i = 1 ... N) in a function definition*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Thu, 29 Jul 2004 07:45:03 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 7/27/04 at 7:00 AM, 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 ...? Thanks Rainer Rather than use Sum I would define MyFunc as follows MyFunc[n_]:=Total@Take[MyData, n] (* using version 5.0 *) or MyFunc[n_]:=Tr@Take[MyData, n] or MyFunc[n_]:=Plus@@Take[MyData, n] -- To reply via email subtract one hundred and four