Cartopy bug?

[Ivan Paspaldzhiev]

Hello,

I'm trying to do something very simple:

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
ax = plt.axes(projection = ccrs.Geodetic())

Yet:

TypeError                                 Traceback (most recent call last)
<ipython-input-4-465130cc1897> in <module>()
----> 1 ax = plt.axes(projection = ccrs.Geodetic())


C:\Users\Ivan\Anaconda2\lib\site-packages\matplotlib\pyplot.pyc in axes(*args, **kwargs)
    865     nargs = len(args)
    866     if len(args) == 0:
--> 867         return subplot(111, **kwargs)
    868     if nargs > 1:
    869         raise TypeError('Only one non keyword arg to axes allowed')


C:\Users\Ivan\Anaconda2\lib\site-packages\matplotlib\pyplot.pyc in subplot(*args, **kwargs)
   1020
   1021     fig = gcf()
-> 1022     a = fig.add_subplot(*args, **kwargs)
   1023     bbox = a.bbox
   1024     byebye = []


C:\Users\Ivan\Anaconda2\lib\site-packages\matplotlib\figure.pyc in add_subplot(self, *args, **kwargs)
    985         else:
    986             projection_class, kwargs, key = process_projection_requirements(
--> 987                 self, *args, **kwargs)
    988
    989             # try to find the axes with this key in the stack


C:\Users\Ivan\Anaconda2\lib\site-packages\matplotlib\projections\__init__.pyc in process_projection_requirements(figure, *args, **kwargs)
    102     else:
    103         raise TypeError('projection must be a string, None or implement a '
--> 104                             '_as_mpl_axes method. Got %r' % projection)
    105
    106     # Make the key without projection kwargs, this is used as a unique


TypeError: projection must be a string, None or implement a _as_mpl_axes method. Got <cartopy._crs.Geodetic object at 0x000000000625D410>

The same type of error happens for projections Geocentric, Globe and LinearRing, from the ones I tried, if that is of any help? Most others (PlateCarree, Mercator, Robinson etc.) work fine. However, I specifically need Geodetic.

What I'm trying to do is I have data that is on a rotated pole grid (EURO-CORDEX data) and I want to subset a region defined by regular lat-lon coordinates. I used this question to convert my regular lat-lon bounding box edges to my data's coordinate system and what I want to now do is mask out the data in the bounding box and plot the result, so I can see if the location I've subset is the one I actually want. 

I can't see what I'm doing wrong here?

Cheers

Ivan

[Ivan Paspaldzhiev]

Forgot to add, Cartopy 0.13.1, IPython 4.0.3.

[pp-mo]

Geodetic and Geocentric etc are coordinate reference systems (CRS), they are not projections.
That is, they don't relate geographical locations to positions on a flat 2d plane.

The classes that work with matlplotlib are the various subclasses of "cartopy.crs.Projection".
These also inherit from CRS, but add extra functions.

For a plot whose coordinates are linear latitude and longitude values you want PlateCarree (aka Equidistant Cylindrical) .

[pp-mo]

I just realised it is stated here :

http://scitools.org.uk/cartopy/docs/latest/crs/index.html

Towards the bottom:

There are a few non-Projection subclasses. [[of CRS]]

These represent coordinate reference systems which are 3 dimensional and could not be drawn directly on a piece of paper.
 . . .