mistake at plot?

mistake at plot?

asked 2011-08-24 17:14:32 +0200

milofis

15 ●1 ●5

updated 2011-08-24 22:47:25 +0200

niles
4519 ●23 ●72 ●132 http://nilesjohnson.net/

what is the meaning of:

verbose 0 (4075: plot.py, generate_plot_points) WARNING: When plotting, failed to evaluate function at 121 points. verbose 0 (4075: plot.py, generate_plot_points) Last error message: ''

when I try to do:

sage: var ('z,t')
(z, t)

sage: z = function ('z',t)

sage: z = 1/2*sqrt(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3/(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 135618210615234381652297748904336450246503209398960128) - sqrt(214447136422061920166015625*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^6 + 3864549077638520528470870886005025216199885162842192609280000000000*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 54181888058488411888503596938295863676921476134912455624013826749306153335312612762848157900410211283238912)/(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 135618210615234381652297748904336450246503209398960128) - 135618210615234381652297748904336450246503209398960128/(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 135618210615234381652297748904336450246503209398960128))

sage:  plot (z, (t, 1,6000))

verbose 0 (4075: plot.py, generate_plot_points) WARNING: When plotting, failed to evaluate function at 121 points.
verbose 0 (4075: plot.py, generate_plot_points) Last error message: ''

answered 2011-08-24 18:04:43 +0200

benjaminfjones
2775 ●8 ●44 ●76 http://bfj7.com/

Your syntax for your function z is badly mangled. Perhaps this is what you want?

sage: z,t = var('z,t')
sage: z = 1/2*sqrt(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3/(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 135618210615234381652297748904336450246503209398960128) - sqrt(214447136422061920166015625*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^6 + 3864549077638520528470870886005025216199885162842192609280000000000*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 54181888058488411888503596938295863676921476134912455624013826749306153335312612762848157900410211283238912)/(14644013671875*(3.55214000000000e12*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 135618210615234381652297748904336450246503209398960128) - 135618210615234381652297748904336450246503209398960128/(5.20175867244141e25*sqrt(t) + 1.97774000000000e13*t^(1/4))^3 - 135618210615234381652297748904336450246503209398960128)

You had a lot of missing * operators and mismatched parentheses.

Assuming what I've posted is the correct function, the warning message from plot is because the values of this function on the interval [1, 6000] are non-real. For example:

sage: z(t=300)
1/2*sqrt(14644013671875*(3.55214000000000e13*sqrt(3) + 1.97774000000000e13*300^(1/4))^3/(14644013671875*(3.55214000000000e13*sqrt(3) + 1.97774000000000e13*300^(1/4))^3 - 135618210615234381652297748904336450246503209398960128) - sqrt(214447136422061920166015625*(3.55214000000000e13*sqrt(3) + 1.97774000000000e13*300^(1/4))^6 + 3864549077638520528470870886005025216199885162842192609280000000000*(3.55214000000000e13*sqrt(3) + 1.97774000000000e13*300^(1/4))^3 - 54181888058488411888503596938295863676921476134912455624013826749306153335312612762848157900410211283238912)/(14644013671875*(3.55214000000000e13*sqrt(3) + 1.97774000000000e13*300^(1/4))^3 - 135618210615234381652297748904336450246503209398960128) - 135618210615234381652297748904336450246503209398960128/(5.20175867244141e26*sqrt(3) + 1.97774000000000e13*300^(1/4))^3 - 135618210615234381652297748904336450246503209398960128)
sage: z(t=300).n()
1.12748264420482e10 + 1.84131889290825e26*I

So you may have the wrong function if you expect to be able to plot it on that interval.

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maybe just missing code formatting, so that *'s are parsed by markdown

niles ( 2011-08-24 22:48:58 +0200 )edit

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