2D plot fails when passing a WCSAxes

[wtbarnes]

Description

When an axis is passed to NDCube.plot, an UnboundLocalErrror is thrown. This appears to be because ax is never actually set if axes is not None in _plot_2D_cube

Expected behavior

A 2D plot.

Actual behavior

---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
<ipython-input-50-663bc3b9d2f3> in <module>
      1 fig = plt.figure()
      2 ax = fig.gca(projection=m)
----> 3 c.plot(**m.plot_settings,axes=ax)

~/anaconda/envs/sunkit-dem/lib/python3.7/site-packages/ndcube/mixins/plotting.py in plot(self, axes, plot_axis_indices, axes_coordinates, axes_units, data_unit, **kwargs)
     81                 if naxis == 2:
     82                     ax = self._plot_2D_cube(axes, plot_axis_indices, axes_coordinates,
---> 83                                             axes_units, data_unit, **kwargs)
     84                 else:
     85                     ax = self._plot_3D_cube(

~/anaconda/envs/sunkit-dem/lib/python3.7/site-packages/ndcube/mixins/plotting.py in _plot_2D_cube(self, axes, plot_axis_indices, axes_coordinates, axes_units, data_unit, **kwargs)
    263                 ax.set_xlabel(xlabel)
    264                 ax.set_ylabel(ylabel)
--> 265         return ax
    266 
    267     def _plot_3D_cube(self, plot_axis_indices=None, axes_coordinates=None,

UnboundLocalError: local variable 'ax' referenced before assignment

Steps to Reproduce

import sunpy.data.sample
import ndcube
import matplotlib.pyplot as plt
m = sunpy.map.Map(sunpy.data.sample.AIA_171_IMAGE)
c = ndcube.NDCube(m.data,m.wcs)
fig = plt.figure()
ax = fig.gca(projection=m)
c.plot(**m.plot_settings,axes=ax)

System Details

• ndcube Version: 1.1.3
• SunPy Version: 1.0.2
• Python Version: 3.7.3
• OS information: macOS 10.14.5 (Mojave)

[DanRyanIrish]

Thanks @wtbarnes. Can you by any chance revert to ndcube 1.1.2 and confirm the same behaviour is produced?

[wtbarnes]

Yep, this error pops up in v1.1.2 as well

[DanRyanIrish]

OK, thanks. We'll add it to the next milestone.