I can confirm that it works for me on OS X with Python 3, gives the error you described with Python 2.
On Thursday, June 6, 2019 at 2:57:08 PM UTC-7, Emmanuel Charpentier wrote: > > According to Serge Lelièvre, the proble doesn't occur when ran under a > Python3-based Sage. He advises to run such a Sage, hich seems a bit early, > IMHO? > > Advice ? > > > Le jeudi 6 juin 2019 11:04:27 UTC+2, Emmanuel Charpentier a écrit : >> >> This ask.sagemath question >> <https://ask.sagemath.org/question/46819/numerical-integration-and-plot-failing/> >> seems >> to raise a genuine bug. Perusing Trac doesn't raise muc relevant, possibly >> except for Trac#24428 <https://trac.sagemath.org/ticket/24428> and >> Trac#21754 <https://trac.sagemath.org/ticket/21754>. >> >> From my comment to the ask.sagemath question : >> >> Indeed : >> sage: var("y,z") >> (y, z) >> sage: cauchy(z)=solve(z*y^3 +y^2 - 2*z*y+2 ,y)[0].rhs() >> sage: def foo(u):return(arg(cauchy(u)).n()) >> sage: [foo(t) for t in (1,1.1..2)] >> [0.828222717321238, >> ## Snip... >> 0.377665318352514] >> Therefore, this function *can* be evaluated. But : >> sage: plot(foo,(1,2)) >> verbose 0 (3635: plot.py, generate_plot_points) WARNING: When >> plotting, failed to evaluate function at 200 points. >> verbose 0 (3635: plot.py, generate_plot_points) Last error message: >> 'negative number cannot be raised to a fractional power' >> Launched png viewer for Graphics object consisting of 0 graphics >> primitives >> ... not in `plot`. Trying to plot symbolically yelds : >> TypeError: Cannot evaluate symbolic expression to a numeric value. >> A bug, IMHO. >> >> Can someone confirm this and, possibly, give me hints as how to flag this >> ticket efficiently ? >> > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/8569d0c8-b910-4c62-8acf-284d8d399ae5%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
