色图编码

Question

我在使用专用色标和底图进行编码时遇到问题

    levels=[35,45,55,65,75,85,95,105,115]
    CB_color_cycle = ['#377eb8', '#ff7f00', '#4daf4a','#f781bf', '#a65628', 
    '#984ea3','#999999', '#e41a1c', '#dede00']
    fig=plt.figure(501)
  m=Basemap(projection='merc',llcrnrlat=27,urcrnrlat=47,llcrnrlon=234,urcrnrlon=285,resolution='h')

    px,py=N.meshgrid(lon+360,lat,sparse="True")
    X,Y=m(px,py)


   m.drawcoastlines()
   m.drawcountries()
   m.drawstates()
   m.fillcontinents(color='gray',alpha=0.1,lake_color='aqua')
   m.drawcounties()


    #plotting contours

 cs=m.contourf(lon+360,lat,tempsfc,levels=levels,cmap=CB_color_cycle,latlon=True,extend='both')
cs2=m.contour(lon+360,lat,tempsfc,levels=levels,latlon=True,colors='k',linestyles='solid')

   cbar=plt.colorbar(cs)
   cbar.add_lines(cs2)
   cbar.ax.set_ylabel('Temp F')

   plt.suptitle("SFC Temperature June 26,2017 at 19Z")
   plt.show()

但是我遇到了这个错误，尽管我有使用 Python 的经验，但我以前从未处理过这个问题，因为我正在尝试使用特殊的色标。

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\mpl_toolkits\basemap\__init__.py:3608: MatplotlibDeprecationWarning: The ishold function was deprecated in version 2.0.
  b = ax.ishold()
C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\mpl_toolkits\basemap\__init__.py:3675: MatplotlibDeprecationWarning: axes.hold is deprecated.
    See the API Changes document (http://matplotlib.org/api/api_changes.html)
    for more details.
  ax.hold(b)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
C:\Users\stratus\Documents\TestforMattsPaper.py in <module>()
     36     #plotting contours
     37 
---> 38 cs=m.contourf(lon+360,lat,tempsfc,levels=levels,cmap=CB_color_cycle,latlon=True,extend='both')
     39 cs2=m.contour(lon+360,lat,tempsfc,levels=levels,latlon=True,colors='k',linestyles='solid')
     40 

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\mpl_toolkits\basemap\__init__.pyc in with_transform(self, x, y, data, *args, **kwargs)
    519             # convert lat/lon coords to map projection coords.
    520             x, y = self(x,y)
--> 521         return plotfunc(self,x,y,data,*args,**kwargs)
    522     return with_transform
    523 

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\mpl_toolkits\basemap\__init__.pyc in contourf(self, x, y, data, *args, **kwargs)
   3671                 mask = np.logical_or(ma.getmaskarray(data),xymask)
   3672                 data = ma.masked_array(data,mask=mask)
-> 3673                 CS = ax.contourf(x,y,data,*args,**kwargs)
   3674         except:
   3675             ax.hold(b)

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\__init__.pyc in inner(ax, *args, **kwargs)
   1890                     warnings.warn(msg % (label_namer, func.__name__),
   1891                                   RuntimeWarning, stacklevel=2)
-> 1892             return func(ax, *args, **kwargs)
   1893         pre_doc = inner.__doc__
   1894         if pre_doc is None:

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\axes\_axes.pyc in contourf(self, *args, **kwargs)
   5827             self.cla()
   5828         kwargs['filled'] = True
-> 5829         contours = mcontour.QuadContourSet(self, *args, **kwargs)
   5830         self.autoscale_view()
   5831         return contours

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\contour.pyc in __init__(self, ax, *args, **kwargs)
    862         self._transform = kwargs.get('transform', None)
    863 
--> 864         self._process_args(*args, **kwargs)
    865         self._process_levels()
    866 

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\contour.pyc in _process_args(self, *args, **kwargs)
   1427                 self._corner_mask = mpl.rcParams['contour.corner_mask']
   1428 
-> 1429             x, y, z = self._contour_args(args, kwargs)
   1430 
   1431             _mask = ma.getmask(z)

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\contour.pyc in _contour_args(self, args, kwargs)
   1518             warnings.warn('Log scale: values of z <= 0 have been masked')
   1519             self.zmin = float(z.min())
-> 1520         self._contour_level_args(z, args)
   1521         return (x, y, z)
   1522 

C:\Users\stratus\AppData\Local\Enthought\Canopy\User\lib\site-packages\matplotlib\contour.pyc in _contour_level_args(self, z, args)
   1184                 warnings.warn("Contour levels are not increasing")
   1185             else:
-> 1186                 raise ValueError("Contour levels must be increasing")
   1187 
   1188     def _process_levels(self):

ValueError: Contour levels must be increasing

缩进不是问题，而是 CB_color_cycle 问题，因为我正试图帮助一位色盲朋友编码。

Answer 1

CB_color_cycle 只是一个颜色列表，所以使用 colors 关键字而不是 cmap:

cs = m.contourf(lon+360, lat, tempsfc, levels=levels, colors=CB_color_cycle, latlon=True, extend='both')

这是关于 contourf docs 中的 colors 关键字的说明：

colors : color string or sequence of colors, optional The colors of the levels, i.e. the lines for contour and the areas for contourf.

The sequence is cycled for the levels in ascending order. If the sequence is shorter than the number of levels, it's repeated.

As a shortcut, single color strings may be used in place of one-element lists, i.e. 'red' instead of ['red'] to color all levels with the same color. This shortcut does only work for color strings, not for other ways of specifying colors.

By default (value None), the colormap specified by cmap will be used.

如果您实际上想做一些涉及真实 ColorMap 的更有趣的事情，请参阅 ListedColorMap or LinearSegmentedColormap (and maybe also ) 的文档以了解有关将颜色列表转换为正确 ColorMap 的详细信息。

色图编码

ColorMap Coding

matplotlib-basemap

colormap