Re: Coefficents of terms in an expression containing the matching string
- To: mathgroup at smc.vnet.net
- Subject: [mg118015] Re: Coefficents of terms in an expression containing the matching string
- From: JJ <wateronwildfire at gmail.com>
- Date: Sat, 9 Apr 2011 07:10:10 -0400 (EDT)
If you wrote your expressions sloppy and they really are
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 - I d3 - I phi]
y2 = 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-I d3-I phi]-0.5*k2^2*k5*v*Exp[-I d2-I d3-I
phi]
Those should work:
(y /. (coeff_*Exp[arg_]) -> coeff) /. Plus -> List
Cases[y2, _*k2^2]
2011/4/7 Chelly <chelly85086 at gmail.com>
> 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)
>