I could be wrong but that problem might relate to the fact that
plotting is often done in floats, which can't handle quantities like
15^1024.  Other types in Sage can handle such things, so you might
have to work around that limitation by plotting the log of the
function or something similar.

-M. Hampton

On Jan 9, 4:11 pm, zieglerk <[email protected]> wrote:
> Thanks, indeed this solved the problem in the example.
>
> Unfortunately, there is still a problem, if the degree of both
> polynomials U and V increases to, say d = 1024.  Note that the degree
> of the rational function P = U/V  is still 0 and both poles (0 and 1)
> are far enough outside of the range where I want to plot.
>
> d = 1024
> R = PolynomialRing(ZZ, x)
> U = x^d + R.random_element(d-1)
> V = x^d - x^(d-1)
> U = expand(U)
> V = expand(V)
> P = U/V
> G = P.plot(2, 15)
> G.show()
>
> returns
>
> verbose 0 (2999: plot.py, generate_plot_points) WARNING: When
> plotting, failed to evaluate function at 5 points.
> verbose 0 (2999: plot.py, generate_plot_points) Last error message: ''
>
> as error message.  And even the option plot_points=5 does not change
> that, although computing several values for P on the interval goes
> smoothely.
>
> Perhaps the problem is, that plot stores the values of P as fractions
> with quite large numerator and denominator, although it would suffice
> to store a numerical approximation -- which is someplace around 1?
>
> Any ideas?
> Konstantin
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