How to plot line graph with x and y categorical axis?

Question

I'm trying to plot a line graph that compares 2 categorical variables. However I keep running into errors. I've put my code below:

import matplotlib.pyplot as plt

cat = ["bored", "happy", "bored", "bored", "happy", "bored"]
dog = ["happy", "happy", "happy", "happy", "bored", "bored"]
activity = ["combing", "drinking", "feeding", "napping", "playing", 
"washing"]

fig, ax = plt.subplots()
ax.plot(activity, dog, label="dog")
ax.plot(activity, cat, label="cat")
ax.legend()

plt.show()

Answer 1

To provide an answer here: When being run with matplotlib >=2.1, the code from the question

import matplotlib.pyplot as plt

cat = ["bored", "happy", "bored", "bored", "happy", "bored"]
dog = ["happy", "happy", "happy", "happy", "bored", "bored"]
activity = ["combing", "drinking", "feeding", "napping", "playing", 
"washing"]

fig, ax = plt.subplots()
ax.plot(activity, dog, label="dog")
ax.plot(activity, cat, label="cat")
ax.legend()

plt.show()

runs fine and produces

---

For earlier versions of matplotlib, axes should be numeric. Hence you need to convert the categories into numbers, plot them, then set the ticklabels accordingly.

 import numpy as np import matplotlib.pyplot as plt cat = ["bored", "happy", "bored", "bored", "happy", "bored"] dog = ["happy", "happy", "happy", "happy", "bored", "bored"] activity = ["combing", "drinking", "feeding", "napping", "playing", "washing"] catu, cati = np.unique(cat, return_inverse=True) dogu, dogi = np.unique(dog, return_inverse=True) fig, ax = plt.subplots() ax.plot(range(len(dog)), dogi, label="dog") ax.plot(range(len(cat)), cati, label="cat") ax.set_xticks(range(len(activity))) ax.set_xticklabels(activity) ax.set_yticks(range(len(catu))) ax.set_yticklabels(catu) ax.legend() plt.show()