Re: problems with parameter lumping using ReplaceAll
- To: mathgroup at smc.vnet.net
- Subject: [mg105880] Re: problems with parameter lumping using ReplaceAll
- From: dh <dh at metrohm.com>
- Date: Wed, 23 Dec 2009 02:40:58 -0500 (EST)
- References: <hgq26v$gck$1@smc.vnet.net>
Hi Sean,
if you do not end: sol=... by a semicolon, mathematica prints the result
of sol=.... Therefore, first you see the un-replaced expression and only
afterwards the replaced one.
Daniel
sean wrote:
> Hello Group,
>
> I have a pretty nasty expression that I'm trying the lump the
> parameters for.
>
> I'm having problems making mathematica perform the following
> replacement.
> Like I said it's pretty nasty and hope it pastes ok.
>
> sol = {{C[0]->p/(-4 a+4 b)+(Sqrt[l^2-m] vd)/(-4 a+4 b)-Sqrt[u-v-2 Sqrt
> [l^2-m] q vd-2 Sqrt[l^2-m] r vd]/(-4 a+4 b),M[0]->-(i/(2 V1-2 V2))-j/
> (2 V1-2 V2)+Sqrt[s^2-4 t]/(2 V1-2 V2)+V1/(2 V1-2 V2)-V2/(2 V1-2 V2),X
> [0]->l/(2 V3-2 V4)+Sqrt[l^2-m]/(2 V3-2 V4)},{C[0]->p/(-4 a+4 b)+(Sqrt
> [l^2-m] vd)/(-4 a+4 b)-Sqrt[u-v-2 Sqrt[l^2-m] q vd-2 Sqrt[l^2-m] r vd]/
> (-4 a+4 b),M[0]->i/(-2 V1+2 V2)+j/(-2 V1+2 V2)+Sqrt[s^2-4 t]/(-2 V1+2
> V2)-V1/(-2 V1+2 V2)+V2/(-2 V1+2 V2),X[0]->l/(2 V3-2 V4)+Sqrt[l^2-m]/(2
> V3-2 V4)},{C[0]->p/(-4 a+4 b)+(Sqrt[l^2-m] vd)/(-4 a+4 b)+Sqrt[u-v-2
> Sqrt[l^2-m] q vd-2 Sqrt[l^2-m] r vd]/(-4 a+4 b),M[0]->-(i/(2 V1-2 V2))-
> j/(2 V1-2 V2)+Sqrt[s^2-4 t]/(2 V1-2 V2)+V1/(2 V1-2 V2)-V2/(2 V1-2 V2),X
> [0]->l/(2 V3-2 V4)+Sqrt[l^2-m]/(2 V3-2 V4)},{C[0]->p/(-4 a+4 b)+(Sqrt
> [l^2-m] vd)/(-4 a+4 b)+Sqrt[u-v-2 Sqrt[l^2-m] q vd-2 Sqrt[l^2-m] r vd]/
> (-4 a+4 b),M[0]->i/(-2 V1+2 V2)+j/(-2 V1+2 V2)+Sqrt[s^2-4 t]/(-2 V1+2
> V2)-V1/(-2 V1+2 V2)+V2/(-2 V1+2 V2),X[0]->l/(2 V3-2 V4)+Sqrt[l^2-m]/(2
> V3-2 V4)},{C[0]->p/(-4 a+4 b)-(Sqrt[l^2-m] vd)/(-4 a+4 b)-Sqrt[u-v+2
> Sqrt[l^2-m] q vd+2 Sqrt[l^2-m] r vd]/(-4 a+4 b),M[0]->-(i/(2 V1-2 V2))-
> j/(2 V1-2 V2)+Sqrt[s^2-4 t]/(2 V1-2 V2)+V1/(2 V1-2 V2)-V2/(2 V1-2 V2),X
> [0]->f/(-2 V3+2 V4)+g/(-2 V3+2 V4)+Sqrt[l^2-m]/(-2 V3+2 V4)-V3/(-2
> V3+2 V4)+V4/(-2 V3+2 V4)},{C[0]->p/(-4 a+4 b)-(Sqrt[l^2-m] vd)/(-4 a+4
> b)-Sqrt[u-v+2 Sqrt[l^2-m] q vd+2 Sqrt[l^2-m] r vd]/(-4 a+4 b),M[0]->i/
> (-2 V1+2 V2)+j/(-2 V1+2 V2)+Sqrt[s^2-4 t]/(-2 V1+2 V2)-V1/(-2 V1+2
> V2)+V2/(-2 V1+2 V2),X[0]->f/(-2 V3+2 V4)+g/(-2 V3+2 V4)+Sqrt[l^2-m]/
> (-2 V3+2 V4)-V3/(-2 V3+2 V4)+V4/(-2 V3+2 V4)},{C[0]->p/(-4 a+4 b)-(Sqrt
> [l^2-m] vd)/(-4 a+4 b)+Sqrt[u-v+2 Sqrt[l^2-m] q vd+2 Sqrt[l^2-m] r vd]/
> (-4 a+4 b),M[0]->-(i/(2 V1-2 V2))-j/(2 V1-2 V2)+Sqrt[s^2-4 t]/(2 V1-2
> V2)+V1/(2 V1-2 V2)-V2/(2 V1-2 V2),X[0]->f/(-2 V3+2 V4)+g/(-2 V3+2
> V4)+Sqrt[l^2-m]/(-2 V3+2 V4)-V3/(-2 V3+2 V4)+V4/(-2 V3+2 V4)},{C[0]->p/
> (-4 a+4 b)-(Sqrt[l^2-m] vd)/(-4 a+4 b)+Sqrt[u-v+2 Sqrt[l^2-m] q vd+2
> Sqrt[l^2-m] r vd]/(-4 a+4 b),M[0]->i/(-2 V1+2 V2)+j/(-2 V1+2 V2)+Sqrt
> [s^2-4 t]/(-2 V1+2 V2)-V1/(-2 V1+2 V2)+V2/(-2 V1+2 V2),X[0]->f/(-2
> V3+2 V4)+g/(-2 V3+2 V4)+Sqrt[l^2-m]/(-2 V3+2 V4)-V3/(-2 V3+2 V4)+V4/
> (-2 V3+2 V4)}}
>
> sol//. 2 V1-2 V2-> 2w/. 2 V3-2 V4 -> 2x//Simplify
>
> If you try it, 2 V1- 2 V2 is only replaced in every other denominator
> in the solutions. (There are 8 equilibrium points in the sol up there)
>
> It also fails to recognize that -V1 + V2 is -w.
>
> Similarly, 2 V3-2 V4 -> 2x fails to replace in some of the
> expressions.
>
> It seems like it has to do with - sign in front of the expression that
> mathematica is trying to make the replacements into. If the expression
> contains the - sign, it doesn't replace the expression.
>
> Question is how do I make the replacements regardless the sign?
>
>
> Thanks much in advance.
>
> Sean
>