Subplots for multiple charts in Data Analysis Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a 2x2 subplot grid with line plots

What is the output of this code that creates a 2x2 grid of line plots with matplotlib?

Data Analysis Python

import matplotlib.pyplot as plt
import numpy as np
x = np.arange(5)
fig, axs = plt.subplots(2, 2)
for i, ax in enumerate(axs.flat):
    ax.plot(x, x*(i+1))
plt.tight_layout()
plt.show()

A A single plot with four lines overlapping, slopes 1 to 4.

B Four line plots arranged in 2 rows and 2 columns, each plot showing lines with slopes 1, 2, 3, and 4 respectively.

C An error because axs.flat is not iterable.

D Four scatter plots arranged in 2 rows and 2 columns.

💡 Hint

Remember that axs.flat lets you iterate over all subplot axes in a grid.

The code creates a 2x2 grid of subplots. The loop uses axs.flat to access each subplot axis and plots a line with slope increasing from 1 to 4. The result is four separate line plots arranged in a 2x2 grid.

❓ data_output

intermediate

Number of subplots created by plt.subplots(3,1)

How many subplot axes are created by the command plt.subplots(3, 1)?

A An error because 3 and 1 are invalid arguments

B 1 subplot axis spanning 3 rows

C 6 subplot axes arranged in 3 rows and 2 columns

D 3 subplot axes arranged vertically

💡 Hint

The first argument is rows, the second is columns.

plt.subplots(3, 1) creates 3 subplot axes arranged vertically in a single column.

❓ visualization

advanced

Identify the subplot layout from the code

Given this code, what is the layout of the subplots shown?

Data Analysis Python

import matplotlib.pyplot as plt
fig, axs = plt.subplots(1, 3, figsize=(9, 3))
for i, ax in enumerate(axs):
    ax.bar([1, 2, 3], [i+1, i+2, i+3])
plt.show()

A Three bar charts side by side in one row

B Three bar charts stacked vertically in one column

C A single bar chart with three bars

D An error because axs is not iterable

💡 Hint

plt.subplots(1, 3) means 1 row and 3 columns.

The code creates a figure with 1 row and 3 columns of subplots. Each subplot shows a bar chart. So the layout is three bar charts side by side.

🔧 Debug

advanced

Why does this subplot code raise an error?

What error does this code raise and why? import matplotlib.pyplot as plt fig, axs = plt.subplots(2, 2) axs[2].plot([1, 2, 3], [4, 5, 6]) plt.show()

A IndexError because axs has shape (2, 2) and index 2 is out of range

B TypeError because axs is not subscriptable

C ValueError because plot data lengths differ

D No error, the plot shows correctly

💡 Hint

axs is a 2D array of axes, not a flat list.

axs is a 2x2 numpy array of axes. Indexing axs[2] tries to access the third row which does not exist, causing IndexError.

🚀 Application

expert

Create a 2x3 grid of scatter plots with different colors

You want to create a 2 rows by 3 columns grid of scatter plots using matplotlib. Each subplot should plot points (x, y) where x = [1,2,3] and y = [3,2,1] multiplied by the subplot index (starting at 1). Each subplot should have a unique color from ['red', 'green', 'blue', 'orange', 'purple', 'brown']. Which code snippet correctly creates this figure?

A

import matplotlib.pyplot as plt
x = [1,2,3]
y = [3,2,1]
colors = ['red', 'green', 'blue', 'orange', 'purple', 'brown']
fig, axs = plt.subplots(2, 3)
for i in range(6):
    axs[i].scatter(x, [v*i for v in y], color=colors[i])
plt.show()

B

import matplotlib.pyplot as plt
x = [1,2,3]
y = [3,2,1]
colors = ['red', 'green', 'blue', 'orange', 'purple', 'brown']
fig, axs = plt.subplots(3, 2)
for i, ax in enumerate(axs.flat):
    ax.scatter(x, [v*i for v in y], color=colors[i])
plt.show()

C

import matplotlib.pyplot as plt
x = [1,2,3]
y = [3,2,1]
colors = ['red', 'green', 'blue', 'orange', 'purple', 'brown']
fig, axs = plt.subplots(2, 3)
for i, ax in enumerate(axs.flat, 1):
    ax.scatter(x, [v*i for v in y], color=colors[i-1])
plt.tight_layout()
plt.show()

D

import matplotlib.pyplot as plt
x = [1,2,3]
y = [3,2,1]
colors = ['red', 'green', 'blue', 'orange', 'purple', 'brown']
fig, axs = plt.subplots(2, 3)
for i, ax in enumerate(axs):
    ax.scatter(x, [v*(i+1) for v in y], color=colors[i])
plt.show()

💡 Hint

Use axs.flat to iterate over all axes in a 2D grid and start index at 1 for multiplication.

Option C correctly creates a 2x3 grid, iterates over all 6 axes with index starting at 1, multiplies y by i, and assigns colors correctly. Other options have wrong shape, indexing, or iteration errors.