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

*To*: mathgroup at smc.vnet.net*Subject*: [mg49704] Re: [mg49666] Using "Sum" (i = 1 ... N) in a function definition*From*: DrBob <drbob at bigfoot.com>*Date*: Thu, 29 Jul 2004 07:43:17 -0400 (EDT)*References*: <200407271100.HAA11129@smc.vnet.net>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

Clear[func] data = {3, 2, 4, 5, 6} func[i_] /; 1 <= i <= Length[data] := Tr[Take[data, i]] {3, 2, 4, 5, 6} func /@ Range[6] {3, 5, 9, 14, 20, func[6]} You can also make the dependence on "data" explicit in various ways (highly recommended). For instance, ClearAll@func data={3,2,4,5,6}; func[data_List][i_Integer]/;1â?¤iâ?¤Length[data]:=Tr[Take[data,i]] func[data]/@Range[6] {3,5,9,14,20,func[{3,2,4,5,6}][6]} Bobby On Tue, 27 Jul 2004 07:00:44 -0400 (EDT), Rainer <wilhelm.rainer at gmx.net> 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 > > > -- DrBob at bigfoot.com www.eclecticdreams.net

**References**:**Using "Sum" (i = 1 ... N) in a function definition***From:*wilhelm.rainer@gmx.net (Rainer)