Support rendering of cftime time axes

proplot doesn't seem to know how to handle cftime too well, which is increasingly more common in xarray now and can handle various climate model calendars, making it pretty useful.

It looks like the auto-generated datetime axis fails and tries to fill in every single time step:

import numpy as np
import proplot as plot
import xarray as xr

datetime = np.arange('1990-01', '2000-01', dtype='datetime64[M]')
cftime = xr.cftime_range('1990-01', '2000-01', freq='M')
da_datetime = xr.DataArray(np.random.rand(len(datetime)), dims='time', coords=[datetime])
da_cftime = xr.DataArray(np.random.rand(len(cftime)), dims='time', coords=[cftime])

f, ax = plot.subplots()
%time ax.plot(da_datetime.time, da_datetime)

f, ax = plot.subplots()
%time ax.plot(da_cftime.time, da_cftime)

Timing comes out essentially equivalent but the latter hangs for 10-15 seconds, probably trying to render the image in the notebook.

Yikes. Thanks for the report, will try to get to this soon

It looks like this is not supported natively by matplotlib. Do you get the same result?

import matplotlib.pyplot as plt
import numpy as np
f, ax = plt.subplots()
ax.plot(cftime, np.random.rand(len(cftime)))

...results in:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-30-37897cbb2798> in <module>
----> 1 f, ax = plt.subplots(); ax.plot(cftime, np.random.rand(len(cftime)))

~/miniconda3/lib/python3.7/site-packages/matplotlib/axes/_axes.py in plot(self, scalex, scaley, data, *args, **kwargs)
   1666         lines = [*self._get_lines(*args, data=data, **kwargs)]
   1667         for line in lines:
-> 1668             self.add_line(line)
   1669         self.autoscale_view(scalex=scalex, scaley=scaley)
   1670         return lines

~/miniconda3/lib/python3.7/site-packages/matplotlib/axes/_base.py in add_line(self, line)
   1900             line.set_clip_path(self.patch)
   1901
-> 1902         self._update_line_limits(line)
   1903         if not line.get_label():
   1904             line.set_label('_line%d' % len(self.lines))

~/miniconda3/lib/python3.7/site-packages/matplotlib/axes/_base.py in _update_line_limits(self, line)
   1922         Figures out the data limit of the given line, updating self.dataLim.
   1923         """
-> 1924         path = line.get_path()
   1925         if path.vertices.size == 0:
   1926             return

~/miniconda3/lib/python3.7/site-packages/matplotlib/lines.py in get_path(self)
   1025         """
   1026         if self._invalidy or self._invalidx:
-> 1027             self.recache()
   1028         return self._path
   1029

~/miniconda3/lib/python3.7/site-packages/matplotlib/lines.py in recache(self, always)
    668         if always or self._invalidx:
    669             xconv = self.convert_xunits(self._xorig)
--> 670             x = _to_unmasked_float_array(xconv).ravel()
    671         else:
    672             x = self._x

~/miniconda3/lib/python3.7/site-packages/matplotlib/cbook/__init__.py in _to_unmasked_float_array(x)
   1388         return np.ma.asarray(x, float).filled(np.nan)
   1389     else:
-> 1390         return np.asarray(x, float)
   1391
   1392

~/miniconda3/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order)
     83
     84     """
---> 85     return array(a, dtype, copy=False, order=order)
     86
     87

~/miniconda3/lib/python3.7/site-packages/pandas/core/indexes/base.py in __array__(self, dtype)
    660         The array interface, return my values.
    661         """
--> 662         return np.asarray(self._data, dtype=dtype)
    663
    664     def __array_wrap__(self, result, context=None):

~/miniconda3/lib/python3.7/site-packages/numpy/core/_asarray.py in asarray(a, dtype, order)
     83
     84     """
---> 85     return array(a, dtype, copy=False, order=order)
     86
     87

TypeError: float() argument must be a string or a number, not 'cftime._cftime.DatetimeGregorian'

I don't have time to check on this right now, but I think that may be that you need to install nc-time-axis (https://github.com/SciTools/nc-time-axis). You usually need to install that to get cftime objects in xarray datasets to plot with their xarray.Dataset.plot() command.

Note that I have that installed in my environment and was still getting issues with proplot. So it didn't extend through to proplot.

I discovered the problem; will close this soon.

I decided to also release a new version (v0.5.0), which includes Fabio's colormaps and this fix. Feel free to update.

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Support rendering of `cftime` time axes #103

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Support rendering of cftime time axes #103

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lukelbd commented on Jan 9, 2020

lukelbd commented on Feb 10, 2020

bradyrx commented on Feb 10, 2020

bradyrx commented on Feb 10, 2020

lukelbd commented on Feb 10, 2020

lukelbd commented on Feb 11, 2020

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Support rendering of `cftime` time axes #103