Re: Help please: Summing a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg13492] Re: Help please: Summing a list*From*: "Allan Hayes" <hay at haystack.demon.cc.uk>*Date*: Fri, 31 Jul 1998 04:33:13 -0400*References*: <6pebm8$i6j@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

robpetersonSPAMME at iname.com wrote in message <6pebm8$i6j at smc.vnet.net>... >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? > >Thanks, Rob > Rob: lst = {a,b,c,d,e}; FoldList[Plus, 0, lst] {0,a,a+b,a+b+c,a+b+c+d,a+b+c+d+e} Rest[%] {a,a+b,a+b+c,a+b+c+d,a+b+c+d+e} Please note that in order to use a definition like PP[[i]]:=Sum[P[[n]],{n,0,i}] PP must have already been define in the fashion PP = ... (notPP:=..) as having the appropriate number of elements. Allan ------------------------------------------------------------- Allan Hayes Training and Consulting Leicester UK http://www.haystack.demon.co.uk hay at haystack.demon.co.uk voice: +44 (0)116 271 4198 fax: +44(0)116 271 8642