Geopandas Userdefined Color Scheme Drops Colors

I expected to get a legend of the three colors green, yellow and red, even if the bottom range is empty (no numbers below 10). Instead GeoPandas drops the yellow color and uses gre

Solution 1:

I was able to fix this issue by setting the norm Parameter:

import pandas as pd
import geopandas
from matplotlib.colors import ListedColormap
from matplotlib.colors import Normalize

colors = ['green', 'yellow', 'red']
bins = [10, 30]
numbers = [15, 25, 35, 35, 55]

ny = geopandas.read_file(geopandas.datasets.get_path('nybb'))
numbers = pd.Series(numbers, name='numbers')
ny = pd.concat([ny, numbers], axis=1)
ny.plot(
    legend=True,
    column='numbers',
    scheme="user_defined",
    cmap=ListedColormap(colors),
    classification_kwds={ 'bins': bins,  },
    norm=Normalize(0, len(colors)),
)

I don't fully know what I am doing here. Basically I think I prevent the default behaviour of normalization of the range of colors to a reduced range of numbers. It's a mixture of understanding the source code and plain trial and error. At least it works for my needs.