Re: Eliminating Annoying Minus Signs

*To*: mathgroup at smc.vnet.net*Subject*: [mg58768] Re: [mg58756] Eliminating Annoying Minus Signs*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Sun, 17 Jul 2005 13:03:13 -0400 (EDT)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

test={-((2*x)/(-1+z)),-((2*y)/(-1+z)),-1}; FullSimplify[test,ComplexityFunction:>(Count[{#},_Times[_Negative,__],?]&)] {(2*x)/(1 - z), (2*y)/(1 - z), -1} However, this will likely be undone by any subsequent use of simplification with the default ComplexityFunction %//Simplify {-((2*x)/(z - 1)), -((2*y)/(z - 1)), -1} Bob Hanlon > > From: "David Park" <djmp at earthlink.net> To: mathgroup at smc.vnet.net > Date: 2005/07/17 Sun AM 03:04:06 EDT > Subject: [mg58768] [mg58756] Eliminating Annoying Minus Signs > > Here is an expression that has annoying minus signs in it. > > test = {-((2*x)/(-1 + z)), -((2*y)/(-1 + z)), -1}; > > We can get rid of them with the following operation. > > MapAt[Minus, test, {{1, 1}, {1, 3, 1}, {2, 1}, {2, 3, 1}}] > {(2*x)/(1 - z), (2*y)/(1 - z), -1} > > But it involves ferreting out the two positions at which we want to change signs and so is a little tedious and error prone. > > Does someone have a simpler method for simplifying such expressions, which occur quite often with Mathematica? > > David Park > djmp at earthlink.net > http://home.earthlink.net/~djmp/ > >