Uncaught error in plotting

[astrojuanlu]

This code:

from poliastro.bodies import Sun
from poliastro.ephem import Ephem
from poliastro.plotting import OrbitPlotter2D

epochs = time_range(..., end=...)  # TBC
earth = Ephem.from_body(Earth, epochs)

plotter = OrbitPlotter2D()

plotter.set_attractor(Sun)
plotter.plot_ephem(earth)

Causes this error:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-130-a5728741413f> in <module>
      2 
      3 plotter.set_attractor(Sun)
----> 4 plotter.plot_ephem(earth)

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/core.py in plot_ephem(self, ephem, epoch, label, color, trail)
    118 
    119         """
--> 120         super().plot_ephem(ephem, epoch, label=label, color=color, trail=trail)
    121 
    122         if not self._figure._in_batch_mode:

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/_base.py in plot_ephem(self, ephem, epoch, label, color, trail)
    286         # Do not return the result of self._plot
    287         # This behavior might be overriden by subclasses
--> 288         self._plot_ephem(ephem, epoch, label=label, color=color, trail=trail)
    289 
    290 

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/_base.py in _plot_ephem(self, ephem, epoch, label, color, trail)
    200             r0 = None
    201 
--> 202         return self.__add_trajectory(
    203             coordinates, r0, label=str(label), colors=colors, dashed=False
    204         )

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/_base.py in __add_trajectory(self, coordinates, position, label, colors, dashed)
    119         self._trajectories.append(trajectory)
    120 
--> 121         self._redraw_attractor()
    122 
    123         trace_coordinates, trace_position = self.__plot_coordinates_and_position(

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/_base.py in _redraw_attractor(self)
     77         self._clear_attractor()
     78 
---> 79         self._draw_sphere(
     80             self._attractor_radius, color, self._attractor.name,
     81         )

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/core.py in _draw_sphere(self, radius, color, name, center)
    275 
    276     def _draw_sphere(self, radius, color, name, center=[0, 0, 0] * u.km):
--> 277         x_center, y_center = self._project(
    278             center[None]
    279         )  # Indexing trick to add one extra dimension

~/.pyenv/versions/seminar38/lib/python3.8/site-packages/poliastro/plotting/_base.py in _project(self, rr)
    296 
    297     def _project(self, rr):
--> 298         rr_proj = rr - rr.dot(self._frame[2])[:, None] * self._frame[2]
    299         x = rr_proj.dot(self._frame[0])
    300         y = rr_proj.dot(self._frame[1])

TypeError: 'NoneType' object is not subscriptable

[astrojuanlu]

Prospective contributors: StaticOrbitPlotter avoids this uncaught error by doing this:

poliastro/src/poliastro/plotting/static.py

Lines 106 to 110 in 6ee8e93

	if self._frame is None:
	raise ValueError(
	"A frame must be set up first, please use "
	"set_orbit_frame(orbit) or plot(orbit)"
	)

We should do the same in OrbitPlotter2D, and add a test.

[clacri]

I would like to take care of this issue :) I'm one of the participants of HacktoberfestES and arrived here thanks to @astrojuanlu

[astrojuanlu]

Awesome! All yours @clacri :)