On Tuesday, 25 August 2015 14:18:52 UTC, kcrisman wrote:
>
>
> I tried to plot the polar form of the cartesian equation x=2, polar( r =
>> sec(x) )
>> but the polar_plot() function returns only the vertical axis. Attached is
>> a screenshot of the output.
>>
>
>
> sage: polar_plot(sec(x),(x,0,pi))
>
> What are you expecting to appear, exactly? sec(pi/2) blows up to infinity,
> and in any case you are just plotting a vertical line.
>
> sage: polar_plot(sec(x),(x,0,pi/2))
> /Users/.../sage-6.5/local/lib/python2.7/site-packages/matplotlib-1.3.1-py2.7-macosx-10.7-x86_64.egg/matplotlib/axis.py:1004:
>
> UserWarning: Unable to find pixel distance along axis for interval padding;
> assuming no interval padding needed.
> warnings.warn("Unable to find pixel distance along axis for interval
> padding; assuming no interval padding needed.")
> /Users/.../sage-6.5/local/lib/python2.7/site-packages/matplotlib-1.3.1-py2.7-macosx-10.7-x86_64.egg/matplotlib/axis.py:1011:
>
> UserWarning: Unable to find pixel distance along axis for interval padding;
> assuming no interval padding needed.
> warnings.warn("Unable to find pixel distance along axis for interval
> padding; assuming no interval padding needed.")
>
> I find this plot at least somewhat helpful:
>
> sage: polar_plot(sec(x),(x,-pi/8,pi/8),ticks=[[],None],aspect_ratio='auto')
>
> To sage devs: See http://trac.sagemath.org/ticket/19087 for something
> this uncovered with our new plot "rich repr" stuff.
>
Thanks kcrisman for your comment. It was really helpful. I should have
realised the ouptut was due to the behaviour of the curve near the vertical
asymptote at (pi/2).
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