setting a legend matching the colours in pyplot.scatter

Question

Suppose my data is organized in the following way:

x_values = [6.2, 3.6, 7.3, 3.2, 2.7]
y_values = [1.5, 3.2, 5.4, 3.1, 2.8]
colours = [1, 1, 0, 1, -1]
label         


        

Answer 1

You can always make your own legend as follows:

import matplotlib.pyplot as plt
import matplotlib.patches as mpatches

x_values = [6.2, 3.6, 7.3, 3.2, 2.7]
y_values = [1.5, 3.2, 5.4, 3.1, 2.8]

a = 'red'
b = 'blue'
c = 'yellow'

colours = [a, a, b, a, c]
labels = ["a", "a", "b", "a", "c"]

axis = plt.gca()
axis.scatter(x_values, y_values, c=colours)

# Create a legend
handles = [mpatches.Patch(color=colour, label=label) for label, colour in [('a', a), ('b', b), ('c', c)]]
plt.legend(handles=handles, loc=2, frameon=True)

plt.show()

Which would look like: