Re: Modifying displayed form of an expression?

*To*: mathgroup at smc.vnet.net*Subject*: [mg57149] Re: Modifying displayed form of an expression?*From*: "Peltio" <peltio at trilight.zone>*Date*: Thu, 19 May 2005 03:08:18 -0400 (EDT)*References*: <d6bi6i$moa$1@smc.vnet.net>*Reply-to*: "Peltio" <peltioNOSPAM at despammed.com.invalid>*Sender*: owner-wri-mathgroup at wolfram.com

"AES" wrote >I have a number of symbolic results which emerge from a Mathematica >calculation in the form > > a Exp[b] > f = ---------------------------------- > Exp[c] - Exp[d] > >where a is "other stuff" and b, c and d are simple sums like b = b1 + b2 >+ b3. By default Mathematica seems to shuffle the elements of b, c and >d in these results such that there will be only positive signs in the >exponents b, c and d. > >I want to force Mathematica to display each of these expressions in the >form > > a Exp[b - c] > ------------------------------------------- > 1 - Exp[d - c] > [snip] >I've been trying Inputs like > > (Exp[-c] Numerator[f]) / (Exp[-c] Denominator[f]) > >and not getting anywhere. > >Ideas? How about Simplify[Numerator[f] Exp[-c]]/Simplify[Denominator[f] Exp[-c]] ? It can be streamlined in a simple procedure, like this: myCollect[fac_][f_] := Simplify[Numerator[f] fac]/Simplify[Denominator[f] fac] So that it can be called like this: f // myCollect[Exp[-c]] A further step would be the identification of the positive signed exponential in the denominator. cheers, Peltio