How do I get multiple subplots in matplotlib?

Question

I am a little confused about how this code works:

fig, axes = plt.subplots(nrows=2, ncols=2)
plt.show()

How does the fig, axes work in this case? What does it do?

Also why wouldn't this work to do the same thing:

fig = plt.figure()
axes = fig.subplots(nrows=2, ncols=2)

Thanks

Answer 1

read the documentation: matplotlib.pyplot.subplots

pyplot.subplots() returns a tuple fig, ax which is unpacked in two variables using the notation

fig, axes = plt.subplots(nrows=2, ncols=2)

the code

fig = plt.figure()
axes = fig.subplots(nrows=2, ncols=2)

does not work because subplots()is a function in pyplot not a member of the object Figure.

Answer 2

There are several ways to do it. The subplots method creates the figure along with the subplots that are then stored in the ax array. For example:

import matplotlib.pyplot as plt

x = range(10)
y = range(10)

fig, ax = plt.subplots(nrows=2, ncols=2)

for row in ax:
    for col in row:
        col.plot(x, y)

plt.show()

However, something like this will also work, it's not so "clean" though since you are creating a figure with subplots and then add on top of them:

fig = plt.figure()

plt.subplot(2, 2, 1)
plt.plot(x, y)

plt.subplot(2, 2, 2)
plt.plot(x, y)

plt.subplot(2, 2, 3)
plt.plot(x, y)

plt.subplot(2, 2, 4)
plt.plot(x, y)

plt.show()

Answer 3

import matplotlib.pyplot as plt

fig, ax = plt.subplots(2, 2)

ax[0, 0].plot(range(10), 'r') #row=0, col=0
ax[1, 0].plot(range(10), 'b') #row=1, col=0
ax[0, 1].plot(range(10), 'g') #row=0, col=1
ax[1, 1].plot(range(10), 'k') #row=1, col=1
plt.show()

Answer 4

You might be interested in the fact that as of matplotlib version 2.1 the second code from the question works fine as well.

From the change log:

Figure class now has subplots method The Figure class now has a subplots() method which behaves the same as pyplot.subplots() but on an existing figure.

Example:

import matplotlib.pyplot as plt

fig = plt.figure()
axes = fig.subplots(nrows=2, ncols=2)

plt.show()

Answer 5

• You can also unpack the axes in the subplots call

• And set whether you want to share the x and y axes between the subplots

Like this:

import matplotlib.pyplot as plt
fig, (ax1, ax2, ax3, ax4) = plt.subplots(2, 2, sharex=True, sharey=True)
ax1.plot(range(10), 'r')
ax2.plot(range(10), 'b')
ax3.plot(range(10), 'g')
ax4.plot(range(10), 'k')
plt.show()