Re: Splitting sums in mathematica

*To*: mathgroup at smc.vnet.net*Subject*: [mg126859] Re: Splitting sums in mathematica*From*: Ray Koopman <koopman at sfu.ca>*Date*: Thu, 14 Jun 2012 05:29:31 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jqusrg$rnm$1@smc.vnet.net> <jr9kqr$3m8$1@smc.vnet.net>

On Jun 13, 2:00 am, "james.a.gordon1" <james.a.gord... at googlemail.com> wrote: > Hi Koopman, > > Thanks for the quick reply, I believe your suggestions solve some > of my problem. To further clarify my question, I have an equation > that looks like this > > F = (X - Y1 - Y2 - Y3 + Z)^2 > > X = Sum_p Sum_q Sum_r [a_p*a_q*a_r] > > Yi = Sum_p Sum_q!=p b_p*b_q, where different X_i have different > terms in the sums > > Z = Sum_p Sum_q!=p Sum_r!=q!=p > > In other words I end up with a large number of terms, each of which > can have as many as 6 nested sums, all of which need to be expanded > resulting in hundreds of terms. I want mathematica to algebraically > expand these nested sums for me rather than me having to type up > the expanded form myself. I believe with your solution I would still > need to manually keep track of the indices for each expansion. > > Once all the nested sums are expanded, I will make some > substitutions of the a, a^2, a^3...a^6 terms, then simplify. > At no point to I need to calculate this with real values, > I just need an algebraic expression. > > Thanks again > > James I don't understand what you're trying to do -- how the Yi differ from one another, or what it means to "make some substitutions of the a, a^2, a^3...a^6 terms", as opposed to substituting for individual terms. Give us a small example, using Mathematica syntax.