如何使用底圖庫在Python的輪廓線上繪制點？

Question

我正在尋找一種在等高線底圖圖中將點繪制到特定值上的簡單方法

這是示例代碼：

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

dx, dy = 0.5, 0.5

# generate 2 2d grids for the x & y bounds
y, x = np.mgrid[slice(-15, 15 + dy, dy),
                slice(-90, -60 + dx, dx)]

z = np.sin(x) + np.cos(5 + y*x) * np.cos(x) + x*y/100
n, m = z.shape
z = z - np.exp(np.random.rand(n,m))

#Setup the map
m = Basemap(projection='merc', llcrnrlat=-15, urcrnrlat=15,\
            llcrnrlon=-90, urcrnrlon=-60, resolution='l')
m.drawcoastlines()

xx, yy = m(x,y)
cs = m.contourf(xx,yy,z,cmap=plt.cm.Spectral_r)
cbar = plt.colorbar(cs, orientation='horizontal', shrink=0.5)

plt.show()

我想在其中a = np.where(abs(z) > 5,np.nan,z)底圖繪制點的情況下，如附圖所示

Answer 1

您可以在第二次調用contourf()使用陰影線 ：

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

dx, dy = 0.5, 0.5

# generate 2 2d grids for the x & y bounds
y, x = np.mgrid[slice(-15, 15 + dy, dy),
                slice(-90, -60 + dx, dx)]

z = np.sin(x) + np.cos(5 + y*x) * np.cos(x) + x*y/100
n, m = z.shape
z = z - np.exp(np.random.rand(n,m))

#Setup the map
m = Basemap(projection='merc', llcrnrlat=-15, urcrnrlat=15,\
            llcrnrlon=-90, urcrnrlon=-60, resolution='l')
m.drawcoastlines()

xx, yy = m(x,y)
cs = m.contourf(xx,yy,z,cmap=plt.cm.Spectral_r)
cbar = plt.colorbar(cs, orientation='horizontal', shrink=0.5)

##adding hatches:
cs = m.contourf(xx, yy, z, levels=[np.min(z),5,np.max(z)], colors='none',
                  hatches=[None,'.',],
                  extend='lower')

plt.show()

給出以下圖像：