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Using lagrange_polynomial() on points with variable coefficients

asked 2023-06-07 02:38:36 +0200

mrutkuokur gravatar image

updated 2023-06-07 13:07:58 +0200

Is it possible to modify lagrange_polynomial so that it accepts points with variable entries? I was able to make it work on a small example, by disabling the coercion functions in the source file "polynomial_ring.py", but then the program failed on a finite field.

y = var("y")
T = PolynomialRing(QQ, 'x')
f = T.lagrange_polynomial([(0,y),(2,2)])
print(f)

returns:

TypeError: unable to convert y to a rational

Documentation for lagrange_polynomial()

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answered 2023-06-07 16:22:17 +0200

Max Alekseyev gravatar image

y must belong to the base ring of the polynomial. Hence a simple fix in this case is to define T over SR rather than QQ:

y = var("y")
T = PolynomialRing(SR, 'x')
f = T.lagrange_polynomial([(0,y),(2,2)])
print(f)
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Asked: 2023-06-07 02:38:36 +0200

Seen: 87 times

Last updated: Jun 07 '23