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"""
Contour labels
--------------
An example of adding contour labels to matplotlib contours.
"""
__tags__ = ['Scalar data']
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
from cartopy.examples.waves import sample_data
def main():
fig = plt.figure()
# Setup a global EckertIII map with faint coastlines.
ax = fig.add_subplot(1, 1, 1, projection=ccrs.EckertIII())
ax.set_global()
ax.coastlines('110m', alpha=0.1)
# Use the waves example to provide some sample data, but make it
# more dependent on y for more interesting contours.
x, y, z = sample_data((20, 40))
z = z * -1.5 * y
# Add colourful filled contours.
filled_c = ax.contourf(x, y, z, transform=ccrs.PlateCarree())
# And black line contours.
line_c = ax.contour(x, y, z, levels=filled_c.levels,
colors=['black'],
transform=ccrs.PlateCarree())
# Uncomment to make the line contours invisible.
# plt.setp(line_c.collections, visible=False)
# Add a colorbar for the filled contour.
fig.colorbar(filled_c, orientation='horizontal')
# Use the line contours to place contour labels.
ax.clabel(
line_c, # Typically best results when labelling line contours.
colors=['black'],
manual=False, # Automatic placement vs manual placement.
inline=True, # Cut the line where the label will be placed.
fmt=' {:.0f} '.format, # Labes as integers, with some extra space.
)
plt.show()
if __name__ == '__main__':
main()
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