当想要在具有不规则分布的模型数据（来自WRF-NMM）的地图上使用matplotlib绘制流线时，我遇到了一个奇怪的问题。
一开始，我正在定义一个新的地图网格：
# Define grid and create map grid
lat = ga.expr('lat') #Latitude from GRIB-File (WRF-NMM), irregularly spaced
lon = ga.expr('lon') #Longitude from GRIB-File (WRF-NMM), irregularly spaced
U10 = ga.expr('ugrd10m')
V10 = ga.expr('vgrd10m')
map = Basemap(projection='cass', lat_0 = 47, lon_0 = 8,
resolution = 'c', llcrnrlon=5.8, llcrnrlat=45.6,
urcrnrlon=10.9, urcrnrlat=48.0,)
longitudes = lon[1,:]
latitudes = lat[:,1]
mx,my = np.meshgrid(longitudes,latitudes)
mapx,mapy = map(mx,my)
# Plot streamlines
stream = map.streamplot(mapx,mapy,U10,V10, density=[0.5, 1])
不幸的是，上面的代码失败了，我无法自己找到错误。这个错误是来自奇怪的网格吗？
以下是错误消息：
/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/contour.py:376: RuntimeWarning: invalid value encountered in true_divide
dist = np.add.reduce(([(abs(s)[i] / L[i]) for i in range(xsize)]), -1)
Traceback (most recent call last):
File "plot_map_v2.py", line 96, in <module>
stream = map.streamplot(mapx,mapy,U10,V10, density=[0.5, 1])
File "/usr/local/lib/python2.7/dist-packages/mpl_toolkits/basemap/__init__.py", line 551, in with_transform
return plotfunc(self,x,y,u,v,*args,**kwargs)
File "/usr/local/lib/python2.7/dist-packages/mpl_toolkits/basemap/__init__.py", line 3691, in streamplot
ret = ax.streamplot(x,y,u,v,*args,**kwargs)
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/axes.py", line 6861, in streamplot
transform=transform)
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/streamplot.py", line 67, in streamplot
grid = Grid(x, y)
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/streamplot.py", line 256, in __init__
assert np.allclose(x_row, x)
AssertionError
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
func(*targs, **kargs)
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/_pylab_helpers.py", line 86, in destroy_all
manager.destroy()
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_gtk3.py", line 427, in destroy
self.canvas.destroy()
AttributeError: FigureManagerGTK3Agg instance has no attribute 'canvas'
Error in sys.exitfunc:
Traceback (most recent call last):
File "/usr/lib/python2.7/atexit.py", line 24, in _run_exitfuncs
func(*targs, **kargs)
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/_pylab_helpers.py", line 86, in destroy_all
manager.destroy()
File "/usr/local/lib/python2.7/dist-packages/matplotlib-1.3.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_gtk3.py", line 427, in destroy
self.canvas.destroy()
AttributeError: FigureManagerGTK3Agg instance has no attribute 'canvas'
干杯，
马丁