Legend

Legend

• Plot legends give meaning to a visualization, assigning labels to the various plot elements. Legends are found in maps - describe the pictorial language or symbology of the map. Legends are used in line graphs to explain the function or the values underlying the different lines of the graph.

• Matplotlib has native support for legends. Legends can be placed in various positions: A legend can be placed inside or outside the chart and the position can be moved. The legend() method adds the legend to the plot.

• To place the legend inside, simply call legend():

import matplotlib.pyplot as plt

import numpy as np

y = [2,4,6,8,10,12,14,16,18,20]

y2 = [10,11,12,13,14,15,16,17,18,19]

x = np.arange(10)

fig = plt.figure()

ax = plt.subplot(111)

ax.plot(x, y, label='$y = numbers')

ax.plot(x, y2, label='$y2 = other numbers')

plt.title('Legend inside')

ax.legend()

plt.show()

Output:

• If we add a label to the plot function, the value will be used as the label in the legend command. There is another argument that we can add to the legend function: We can define the location of the legend inside of the axes plot with the parameter "loc". If we add a label to the plot function, the values will be used in the legend command:

frompolynomialsimportPolynomial

importnumpyasnp

importmatplotlib.pyplotasplt

p=Polynomial(-0.8,2.3,0.5,1,0.2)

p_der=p.derivative()

fig, ax=plt.subplots()

X=np.linspace (-2,3,50, endpoint=True)

F=p(X)

F_derivative=p_der(X)

ax.plot(X,F,label="p")

ax.plot(X,F_derivative,label="derivation of p")

ax.legend(loc='upper left')

Output:

Matplotlib legend on bottom

importmatplotlib.pyplotasplt

importnumpyasnp

y1 = [2,4,6,8,10,12,14,16,18,20]

y2 = [10,11,12,13,14,15,16,17,18,19]

x = np.arange(10)

fig = plt.figure()

ax = plt.subplot(111)

ax.plot(x, y, label='$y = numbers')

ax.plot(x, y2, label='$y2= = other numbers')

plt.title('Legend inside')

ax.legend(loc='upper center', bbox_to_anchor=(0.5, -0.05),  

shadow=True, ncol=2)

plt.show()

Output: