matplotlib 颜色条边界未实现

Question

我正在尝试在一个循环中创建多个具有相同颜色条限制的图。

我用map.contourf(x, y, U_10m, vmin=0, vmax=25) 设置了等高线图的限制，这似乎为每个图提供了一致的色标。但是，当我使用cbar = plt.colorbar(boundaries=np.linspace(0,1,25), ticks=[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24]) # sets all cbar to same limits 时，每个图都没有相同的颜色条限制（下面是具有不同颜色条和代码的两个图的示例）。

 from netCDF4 import Dataset as NetCDFFile
from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import numpy as np

def wrf_tseries_contour_plotter (
ncfile, time_ind, lowerllat, upperrlat, lowerllon, upperrlon, output_dir):
    '''
    EDITED FROM http://www.atmos.washington.edu/~ovens/wrfwinds.html 
    '''

    print 'timestep:', + time_ind 
    #which figure is being generated 0 = 00:00, 144 = 23:50
    nc     = NetCDFFile(ncfile, 'r')
    #
# get the actual longitudes, latitudes, and corners
lons = nc.variables['XLONG'][time_ind]
lats = nc.variables['XLAT'][time_ind]

#get the u10 to plot as a contour instead of t2m
U10_raw = nc.variables['U10'][time_ind] #61 is the index for 10:00am 
V10_raw = nc.variables['V10'][time_ind]

#bodge to calculate U from U and V (u10 = sqrt(u^2+v^2))
v2 = np.square(V10_raw)
u2 = np.square(U10_raw)
U_10m = np.sqrt(u2 + v2)

# Make map
map = Basemap(projection='cyl',llcrnrlat=lowerllat,urcrnrlat=upperrlat,
            llcrnrlon=lowerllon,urcrnrlon=upperrlon,
                resolution='h')
# lllat, urlat,lllon, urlon set outside of f(x) lower left and 
# upper right lat/lon for basemap axis limits

x, y = map(lons[:,:], lats[:,:])
    map.contourf(x, y, U_10m, vmin=0, vmax=25) 
    map.drawcoastlines(linewidth = 0.5, color = '0.15') 
    #thinner lines for larger scale map

    #plt.clim(0, 25) #added
    cbar = plt.colorbar(boundaries=np.linspace(0,1,25), ticks=[0, 2, 4, 6,
    8, 10, 12, 14, 16, 18, 20, 22, 24]) # sets all cbar to same limits
    cbar.set_label('10m U (m/s)', size=12)
    cbar.ax.set_yticklabels([0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24])
    #cbar.set_clim(0, 25)

    time_str = str(time_ind)
    plt.title('gust 20070724' + '_' + time_str)
    fig_name = '\gust20070724_'+  time_str + '.png'      
    plt.savefig(output_dir + fig_name)
    plt.close()
#set inputs for  wrf_tseries_contour_plotter(ncfile, time_ind, lllat, urlat,
                                             lllon, urlon, output_dir)

ncfile = 'E:\WRFout_UK2Fino\wrfout_d03_2007-07-24_00%3A00%3A00'
tlist = np.arange(0,145) 

#set the lower left/upper right lat/lon for axis limits on the maps
lowerllat=48
upperrlat=63
lowerllon=-10
upperrlon=25

#set output directory for figures 
output_dir = '''C:\cbar_test'''

for time_ind in tlist:
    wrf_tseries_contour_plotter(ncfile, time_ind, lowerllat, upperrlat, 
                                lowerllon, upperrlon, output_dir)

Answer 1

您必须使用 vmin 和 vmax 值来设置颜色条的边界，如下例所示：

import numpy as np
import matplotlib.cm as cm
import matplotlib.mlab as mlab
import matplotlib.pyplot as plt

# test data
x = np.linspace(0,15,100)
X,Y = np.meshgrid(x,x)
SPD1 = np.sqrt(X*X + Y*Y)
SPD2 = SPD1 * 1.3

fig = plt.figure()  

# implement boundaries of colorbar and it ticks
vmin, vmax = 0, 26
levels = np.linspace(vmin,vmax,14)

# 1st subplot
ax1 = fig.add_subplot(221)
# Set contour levels and limits
CF1 = ax1.contourf(X, Y, SPD1, levels=levels, vmax=vmax, vmin=vmin) 
cbar = plt.colorbar(CF1)
cbar.set_label('10m U (m/s)', size=12)

#2nd subplot
ax1 = fig.add_subplot(222)
CF1 = ax1.contourf(X, Y, SPD2, levels=levels, vmax=vmax, vmin=vmin) 
cbar = plt.colorbar(CF1)
cbar.set_label('10m U (m/s)', size=12)

plt.tight_layout()
plt.show()

但是，您必须正确选择 vmin、vmax，因为如果您的值超出颜色条的边界，它们将不会显示（第二个子图的右上角）。