How to Add Labels in a Plot using Python?

Prerequisites: Python Matplotlib 

In this article, we will discuss adding labels to the plot using Matplotlib in Python. But first, understand what are labels in a plot. The heading or sub-heading written at the vertical axis (say Y-axis) and the horizontal axis(say X-axis) improves the quality of understanding of plotted stats.

Example: Let’s create a simple plot

Python

# python program to plot graph without labels
import matplotlib
import matplotlib.pyplot as plt
import numpy as np


# it will take x coordinates by default
# starting from 0,1,2,3,4...
y = np.array([3, 8, 1, 10])

plt.plot(y)
plt.show()

Output:

Plot without Labels or Title

Creating Labels for a Plot

By using pyplot() function of library we can add xlabel() and ylabel() to set x and y labels. 

Example: Let’s add Label in the above Plot

Python

# python program for plots with label
import matplotlib
import matplotlib.pyplot as plt
import numpy as np


# Number of children it was default in earlier case
x = np.array([0, 1, 2, 3])

# Number of families
y = np.array([3, 8, 1, 10])

plt.plot(x, y)

# Label for x-axis
plt.xlabel("Number of Childrens")

# Label for y-axis
plt.ylabel("Number of Families")

plt.show()  # for display

Output:

Plot with Labels

If you would like to make it more understandable, add a Title to the plot, by just adding a single line of code.

plt.title("Survey Of Colony")

Example:

Python3

# python program for plots with label
import matplotlib
import matplotlib.pyplot as plt
import numpy as np


# Number of children it was default in earlier case
x = np.array([0, 1, 2, 3])

# Number of families
y = np.array([3, 8, 1, 10])

plt.plot(x, y)

# Label for x-axis
plt.xlabel("Number of Childrens")

# Label for y-axis
plt.ylabel("Number of Families")

# title of the plot
plt.title("Survey Of Colony")

plt.show()  # for display

Output:

Plot with Title

Set Font Properties for Titles and Labels

In order to make the Plot more attractive use the fontdict parameter in xlabel(), ylabel(), and title() to apply the font properties.

Python

# Adding font properties to labels and titles
import matplotlib
import matplotlib.pyplot as plt
import numpy as np


# Number of Children
x = np.array([0, 1, 2, 3])

# Number of Families
y = np.array([3, 8, 1, 10])

# label including this form1 will have these properties
form1 = {'family': 'serif', 'color': 'blue', 'size': 20}

# label including this form2 will have these properties
form2 = {'family': 'serif', 'color': 'darkred', 'size': 15}

plt.plot(x, y)
plt.xlabel("Number of Childrens", fontdict=form1)
plt.ylabel("Number of Families", fontdict=form1)
plt.title("Survey Of Colony", fontdict=form2)
plt.show()

Output:

Plot with Font Properties