Re: Coefficents of terms in an expression containing the matching string
- To: mathgroup at smc.vnet.net
- Subject: [mg118025] Re: Coefficents of terms in an expression containing the matching string
- From: DrMajorBob <btreat1 at austin.rr.com>
- Date: Sat, 9 Apr 2011 07:11:58 -0400 (EDT)
"Id 3" probably should be "I d3", as well. Bobby On Fri, 08 Apr 2011 03:15:06 -0500, Bob Hanlon <hanlonr at cox.net> wrote: > > Use proper Mathematica syntax when writing to the group. > > y = 0.5*u*Exp[-2 I d1 - d2 - I d4 - phi] - > 0.5*k2*k3*u*Exp[-I d2 - I d4 - phi] - > 0.5*k2*k4*u*Exp[-I d2 - Id 3 - I phi]; > > List @@ y /. Exp[_] -> 1 > > {0.5 u, -0.5 k2 k3 u, -0.5 k2 k4 u} > > If you really want to lose the signs then > > List @@ y /. {Exp[_] -> 1, x_?Negative -> -x} > > {0.5 u, 0.5 k2 k3 u, 0.5 k2 k4 u} > > y = 0.5*u*Exp[-2 I d1 - d2 - I d4 - phi] - > 0.5*k2^2*k3*u*Exp[-I d2 - I d4 - phi] - > 0.5*k2*k4*u*Exp[-I d2 - Id 3 - I phi] - > 0.5*k2^2*k5*v*Exp[-I d2 - Id 3 - I phi]; > > Select[y, ! FreeQ[#, k2^2] &] > > -0.5*E^((-I)*d2 - I*d4 - phi)*k2^2*k3*u - > 0.5*E^((-I)*d2 - 3*Id - I*phi)*k2^2*k5*v > > > Bob Hanlon > > ---- Chelly <chelly85086 at gmail.com> wrote: > > ============= > I have two questions. The solutions may be very simple, but since I am a > Mathematica novice, need some guidance. > 1) I have an expression: > y = 0.5*u*exp(-2 I d1 - d2 - I d4 - phi) - > 0.5*k2*k3*u*exp(-I d2 - I d4 - phi) - > 0.5*k2*k4*u*exp(-I d2 - Id 3 - I phi) ; > What command should I use to get just the amplitude of each term, i.e > excluding the exponential - exp(). In this case, the results needs to be > {0.5*u, 0.5*k2*k3*u, 0.5*k2*k4*u) > 2) The second question is along similar lines. I have an expression and > I need to find out the terms that have k2^2 in the amplitude > y = 0.5*u*exp(-2 I d1 - d2 - I d4 - phi) - > 0.5*k2^2*k3*u*exp(-I d2 - I d4 - phi) - > 0.5*k2*k4*u*exp(-I d2 - Id 3 - I phi) - > 0.5*k2^2*k5*v*exp(-I d2 - Id 3 - I phi) ; > In this case, the answer is the second and last term: > 0.5*k2^2*k3*u*exp(-I d2 - I d4 - phi) - > 0.5*k2^2*k5*v*exp(-I d2 - Id 3 - I phi) > > > -- DrMajorBob at yahoo.com