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 Post subject: monomial's coefficient
PostPosted: Mon May 23, 2016 9:36 pm 

Joined: Fri Jun 24, 2011 10:10 am
Posts: 9
friends,
I'm looking for a singular procedure to return a given monomial's coefficient
of a polynomial.

Example poly f = 2 x ^ 3 + 5z^3;
test (f, x ^ 3) // --> 2
test (f, y ^ 3) // --> 0
who can help me?


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 Post subject: Re: monomial's coefficient
PostPosted: Tue May 24, 2016 7:49 am 

Joined: Sat Apr 16, 2016 7:25 pm
Posts: 8
There is 'coeffs' command for this.
ring r = 0,(x,y,z),dp;
poly f = 2 x ^ 3 + 5z^3;
> coeffs(f,x);
_[1,1]=-5z3 //coefficient of x^0
_[2,1]=0 // coeff of x^1
_[3,1]=0 // coeff of x^2
_[4,1]=2 // coeff of x^3

If you need to extract a specific entry from this matrix, directly specify the position,
> coeffs(f,x)[4,1]; //For x^3
2

Similarly for other ring variables. It shouldn't be too difficult to convert it into a function.


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 Post subject: Re: monomial's coefficient
PostPosted: Tue May 24, 2016 4:29 pm 

Joined: Wed May 25, 2005 4:16 pm
Posts: 178
Another possibility is 'coeffs'
(http://www.singular.uni-kl.de/Manual/4-0-3/sing_271.htm)
and a third one:
Code:
jet(f/x^3,0)


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