I was pretty sure, that there was a method for polynomials to extract
the coefficient of a certain monomial (say x^2). But the method I
used for that before
R = PolynomialRing(QQ, 'x')
f = R.random_element(degree = 3)
f.coeff(x^2)
now returns the error
AttributeError: 'Polynomial_rational_dense' object has no attribute
'coeff'
Of course, there is always the workaround by the complete list of
coefficients:
f.coeffs()[2]
but this certainly does not generalize to multivariate polynomials.
The code I was using until very recently (sage 4.3.1 I guess) was like
S = PolynomialRing(QQ, 'x, y')
g = S.random_element(degree = 3)
g.coeff(x^2)
and now returns
AttributeError:
'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular'
object has no attribute 'coeff'
Again, there seems to be a workaround using g.coefficient(), but I am
unable handle this method even with the documentation provided, e.g.
for
g = 2*x*y^2 - 2*y^3 + x^2 + 3*y^2 - 4
g.coefficient({x:0, y:0}) == g
g.coefficient({x:1, y:2}) == g
g.coefficient({x:2, y:2}) == g
are all true?! And
g.coefficient(x^2)
returns the error
TypeError: The input degrees must be a dictionary of variables to
exponents.
although the documentation has as an example
sage: R.<x,y> = QQ[]
sage: f=(1+y+y^2)*(1+x+x^2)
sage: f.coefficient({x:0})
y^2 + y + 1
sage: f.coefficient([0,None])
y^2 + y + 1
sage: f.coefficient(x)
y^2 + y + 1
Am I missing something here?
Thanks,
Konstantin
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