I would guess the problem stems from the
sage: length = daylength.subs(locals()).n()
line somehow. I would recommend making daylength a function, instead
of substituting.
I am still not sure exactly what the problem is in the original code
though.
On Feb 9, 12:35 pm, Stan Schymanski <schym...@gmail.com> wrote:
> Dear all,
>
> For some reason, the meaning of the global constants pi and e (and
> maybe others) becomes unavailable to the plot command in the following
> example. Is this a bug?
>
> ----------------------------------------------------------------------
> | Sage Version 3.2, Release Date: 2008-11-20 |
> | Type notebook() for the GUI, and license() for information. |
> ----------------------------------------------------------------------
>
> sage: var('h delta phi doy t')
> (h, delta, phi, doy, t)
> sage: h = 1/12*pi*(t-12)
> sage: delta = -23.45*pi/180*cos(2*pi*(doy+10)/365)
> sage: sinbeta = cos(h)*cos(delta)*cos(phi)+sin(delta)*sin(phi)
> sage: daylength = 12+24/180*arcsin(tan(phi)*sin(delta)/cos(delta))*180/
> pi
> sage: plot(pi*x,x,0,1)
>
> sage: plot(exp(x),x,0,1)
>
> sage: doy = 180
> sage: phi = (30*pi/180).n()
> sage: length = daylength.subs(locals()).n()
> sage: t0 = 12-0.5*length
> sage: t1 = 12+0.5*length
> sage: plot(pi*x,x,0,1)
> ERROR: An unexpected error occurred while tokenizing input
> The following traceback may be corrupted or invalid
> The error message is: ('EOF in multi-line statement', (546, 0))
> [...]
> ValueError: free variable: pi
>
> sage: plot(exp(x),x,0,1)
> [...]
> ValueError: free variable: e
>
> Funnily enough, the following fixes the pi-problem for the time being:
>
> sage: pi=pi.n()
>
> But e=e.n() does not fix the e-problem.
>
> Can anyone help?
>
> Thanks a lot,
> Stan
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