CEA projection: plotting all the data works, plotting part of the data fails.

Using the following setup, Python 2.7/matplotlib 1.2.1/basemap 1.0.6

from mpl_toolkits import basemap

m1 = basemap.Basemap(projection='cea', lon_0=0)
lon = [-135, -45, 45, 135]
lat = [45, 45, 45, 45]

If I then run the following command, the line plots as expected:

m1.plot(lon, lat, latlon=True)

But plotting just the first two points alone gives a failure:

m1.plot(lon[:2], lat[:2], latlon=True)

Here's the result:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-273-c6f75eb64ab8> in <module>()
      8 lat = [45, 45, 45, 45]
      9 #m1.plot(lon, lat, latlon=True)
---> 10 m1.plot(lon[:2], lat[:2], latlon=True)

/Users/jakevdp/anaconda/python.app/Contents/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.pyc in with_transform(self, x, y, *args, **kwargs)
    525             if self.projection in _cylproj or self.projection in _pseudocyl:
    526                 if x.ndim == 1:
--> 527                     x = self.shiftdata(x)
    528                 elif x.ndim == 0:
    529                     if x > 180:

/Users/jakevdp/anaconda/python.app/Contents/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.pyc in shiftdata(self, lonsin, datain, lon_0)
   4700             londiff = np.abs(lonsin[0:-1]-lonsin[1:])
   4701             londiff_sort = np.sort(londiff)
-> 4702             thresh = 360.-londiff_sort[-2]
   4703             itemindex = len(lonsin)-np.where(londiff>=thresh)[0]
   4704             if itemindex:

IndexError: index -2 is out of bounds for axis 0 with size 1

Edit: here's an error from a similar call, but I believe it's unrelated to the first:

lat = [-45, 45, 45, 45, 45, 0]
lon = [135, -135, -45, 45, 135, -90]
m1.plot(lon, lat, latlon=True)

error:

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-295-d815d338a0b6> in <module>()
     11 lon = [135, -135, -45, 45, 135, -90]
     12 
---> 13 m1.plot(lon, lat, latlon=True)
     14 

/Users/jakevdp/anaconda/python.app/Contents/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.pyc in with_transform(self, x, y, *args, **kwargs)
    525             if self.projection in _cylproj or self.projection in _pseudocyl:
    526                 if x.ndim == 1:
--> 527                     x = self.shiftdata(x)
    528                 elif x.ndim == 0:
    529                     if x > 180:

/Users/jakevdp/anaconda/python.app/Contents/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.pyc in shiftdata(self, lonsin, datain, lon_0)
   4702             thresh = 360.-londiff_sort[-2]
   4703             itemindex = len(lonsin)-np.where(londiff>=thresh)[0]
-> 4704             if itemindex:
   4705                 # check to see if cyclic (wraparound) point included
   4706                 # if so, remove it.

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Reproduce los dos ejemplos con la configuración de Python 2.7, matplotlib 1.2.1 y Basemap 1.0.6; después, inspecciona mpl_toolkits/basemap/init.py alrededor de los puntos de entrada m1.plot transform y shiftdata que se muestran en el traceback. Se considera terminado cuando el trazado del subconjunto de dos puntos se realiza correctamente y el ejemplo relacionado de múltiples puntos ya no genera los errores de indexación o de valor booleano indicados.