RE: Extracting polynomial coefficients?
- To: mathgroup@smc.vnet.net
- Subject: [mg11533] RE: [mg11464] Extracting polynomial coefficients?
- From: jmt <jmthomas@cybercable.tm.fr>
- Date: Sat, 14 Mar 1998 13:55:52 -0500
- Organization: TeA
Try this:
p=4 a^2 b^3 c + r q d^5 + a d^3 + q c^2 a^2 + r^2 a d^3
allVariables=Variables[p]
myConstants={r,q}
myVariables=Complement[allVariables,myConstants] FullForm[p](*this to
explain the following replacement rules*)
np=p/.Flatten[{Plus->List,Times[y_?IntegerQ,z_]->z,Map[(#->1)&,myConstants]}]
Map[{#,Coefficient[p,#]}&,np]
Hope this helps,
----------------------------------------------- Jean-Marie THOMAS
Conseil et Audit en Ingenierie de Calcul www.cybercable.tm.fr/~jmthomas
------------------------------------------------
-----Message d'origine-----
De: Thomas Bell [SMTP:tombell@leland.Stanford.EDU] Date: jeudi 12 mars
1998 07:35
A: mathgroup@smc.vnet.net
Objet: [mg11464] Extracting polynomial coefficients?
I have a very long polynomial that's a function of four variables, a, b,
c, d. I would like Mathematica to (1) tell me what combinations of a,
b, c, and d are in my polynomial, and (2) tell me what the coefficients
are for each of the variable terms.
For example, say I have constant terms r and q. My polynomial might
look something like
4 a^2 b^3 c + r q d^5 + a d^3 + q c^2 a^2 + r^2 a d^3
I would like to have Mathematica output something like:
a^2 b^3 => 4
d^5 => r q
a d^3 => 1 + r^2
c^2 a^2 => q
The polynomial is long enough that it would be very time-consuming to
search through and identify all the combinations of (a,b,c,d).
Any help appreciated. Thanks.
-------------------------------------------------------------- Thomas
(Tom) Bell Gravity Probe-B, H.E.P.L. tombell@stanford.edu Stanford
University 136D Escondido Village Stanford, CA 94305-4085 Stanford, CA
94305 650/725-6378 (o) 650/497-4230 (h) 650/725-8312 (fax)