Re: automatic coefficient / summand extraction
- To: mathgroup at yoda.physics.unc.edu
- Subject: Re: automatic coefficient / summand extraction
- From: sergio at shark.inst.bnl.gov (Sergio Rescia)
- Date: Thu, 21 Oct 93 15:09:56 EDT
Dear Axel,
Here is one way.
First look at the "internal" form of your expression:
In[35]:= expr=Expand[5 a + 3 b + (2 c + 5 a) / 7]
40 a 2 c
Out[35]= ---- + 3 b + ---
7 7
Note terms are in alphabetical order.
In[36]:= FullForm[expr]
Out[36]//FullForm=
> Plus[Times[Rational[40, 7], a], Times[3, b], Times[Rational[2, 7], c]]
In[37]:= Length[expr]
Out[37]= 3
It is now clear that one simple way to have your coefficient list is:
In[38]:= Table[expr[[i,1]],{i,1,Length[expr]}]
40 2
Out[38]= {--, 3, -}
7 7
or better:
In[39]:= Table[{expr[[i,2]],expr[[i,1]]},{i,1,Length[expr]}]
40 2
Out[39]= {{a, --}, {b, 3}, {c, -}}
7 7
Regards,
Sergio
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