Individual subplot customization in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of subplot title customization

What will be the title of the second subplot after running this code?

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(1, 2)
axs[0].set_title('First Plot')
axs[1].set_title('Second Plot')
plt.close(fig)
print(axs[1].get_title())

A Second Plot

B First Plot

C Plot 2

D null

💡 Hint

Check which subplot index is used to set the title.

The code sets the title of axs[1] to 'Second Plot'. The print statement outputs this exact string.

❓ data_output

intermediate

Number of ticks on customized subplot

After running this code, how many x-axis ticks will the first subplot display?

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(2, 1)
axs[0].set_xticks([0, 1, 2, 3])
axs[1].set_xticks([0, 1])
plt.close(fig)
print(len(axs[0].get_xticks()))

A 4

B 2

C 5

D 3

💡 Hint

Count the number of positions passed to set_xticks for the first subplot.

The first subplot has ticks set at [0,1,2,3], so it will have 4 ticks.

❓ visualization

advanced

Identify subplot with customized grid style

Which subplot will display a dashed grid after running this code?

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(1, 3)
axs[0].grid(true, linestyle='--')
axs[1].grid(true, linestyle=':')
axs[2].grid(true, linestyle='-')
plt.close(fig)
print([axs[i].get_xgridlines()[0].get_linestyle() for i in range(3)])

A First subplot

B Second subplot

C Third subplot

D null of them

💡 Hint

Look at the linestyle argument passed to grid for each subplot.

The first subplot uses linestyle='--' which is dashed. The others use dotted ':' and solid '-'.

🔧 Debug

advanced

Identify error in subplot label customization

What error will this code raise when customizing subplot labels?

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(2, 2)
axs[0].set_xlabel('X axis')
axs[1].set_ylabel('Y axis')
axs[4].set_title('Invalid subplot')
plt.close(fig)

A IndexError

B AttributeError

C TypeError

D No error

💡 Hint

Check the index used to access axs array.

axs is a 2x2 array, so valid indices are 0 to 3. axs[4] is out of range causing IndexError.

🚀 Application

expert

Customize individual subplot background colors

Given this code, which option correctly sets the background color of the middle subplot to light gray?

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(1, 3)
# Customize background color here
plt.close(fig)

A axs[1].set_facecolor('lightgray')

B axs[1].set_background('lightgray')

C axs[1].facecolor = 'lightgray'

D axs[1].background_color('lightgray')

💡 Hint

Use the correct method to set the axes background color.

The correct method to set the background color of a subplot is set_facecolor(). Other options are invalid or do not exist.

Practice

1. What is the correct way to change the title of the second subplot when using fig, axs = plt.subplots(2, 2)?

easy

A. Use plt.title('New Title')

B. Use axs[1].set_title('New Title')

C. Use fig.set_title('New Title')

D. Use axs[0, 1].set_title('New Title')

Solution

1. Step 1: Understand subplot indexing

   With plt.subplots(2, 2), axs is a 2x2 array. The second subplot in the first row is at position [0, 1].

2. Step 2: Set title for specific subplot

   Use axs[0, 1].set_title('New Title') to change only that subplot's title.

3. Final Answer:

   Use axs[0, 1].set_title('New Title') -> Option D

4. Quick Check:

   Indexing subplots by row and column = A [OK]

Hint: Use axs[row, col] to target specific subplot [OK]

Common Mistakes:

• Using axs[1] instead of axs[0, 1]
• Setting title on fig instead of axs
• Using plt.title affects whole figure, not subplot

2. Which of the following is the correct syntax to change the x-axis label of the first subplot in a 1D array of subplots fig, axs = plt.subplots(3)?

easy

A. axs[1].set_xlabel('X Label')

B. axs[0].set_xlabel('X Label')

C. axs.set_xlabel('X Label')

D. fig.set_xlabel('X Label')

Solution

1. Step 1: Identify subplot indexing in 1D array

   With plt.subplots(3), axs is a 1D array with indices 0, 1, 2. The first subplot is at index 0.

2. Step 2: Use set_xlabel on the correct subplot

   Use axs[0].set_xlabel('X Label') to set the x-axis label of the first subplot.

3. Final Answer:

   axs[0].set_xlabel('X Label') -> Option B

4. Quick Check:

   Index 0 for first subplot in 1D axs = D [OK]

Hint: Remember 1D axs uses zero-based indexing [OK]

Common Mistakes:

• Using axs[1] for first subplot
• Calling set_xlabel on fig or axs directly
• Confusing 1D and 2D axs indexing

3. What will be the color of the line in the third subplot after running this code?

import matplotlib.pyplot as plt
fig, axs = plt.subplots(2, 2)
axs[1, 0].plot([1, 2, 3], [4, 5, 6], color='green')
plt.show()

medium

A. Blue

B. Red

C. Green

D. Black

Solution

1. Step 1: Identify subplot position

   With plt.subplots(2, 2), subplots are indexed as [0,0], [0,1], [1,0], [1,1]. The third subplot is at [1,0].

2. Step 2: Check plot color argument

   The code sets color='green' for the line in subplot [1,0].

3. Final Answer:

   Green -> Option C

4. Quick Check:

   Color set explicitly to green = B [OK]

Hint: Check subplot index and color argument carefully [OK]

Common Mistakes:

• Assuming default blue color
• Confusing subplot index order
• Ignoring color parameter in plot

4. Identify the error in this code that tries to set the y-axis label of the last subplot:

fig, axs = plt.subplots(2, 2)
axs[2, 1].set_ylabel('Y Label')

medium

A. IndexError because axs has shape (2,2) and index (2,1) is out of range

B. AttributeError because set_ylabel is not a valid method

C. SyntaxError due to wrong indexing syntax

D. No error, code runs fine

Solution

1. Step 1: Check axs shape and indexing

   With plt.subplots(2, 2), axs shape is (2, 2), valid indices are 0 or 1 for each dimension.

2. Step 2: Identify invalid index

   Indexing axs[2, 1] tries to access third row (index 2), which does not exist, causing IndexError.

3. Final Answer:

   IndexError because axs has shape (2,2) and index (2,1) is out of range -> Option A

4. Quick Check:

   Index out of range error = C [OK]

Hint: Check subplot array shape before indexing [OK]

Common Mistakes:

• Assuming axs has more rows than created
• Confusing AttributeError with IndexError
• Using wrong indexing syntax

5. You want to create a 2x2 grid of subplots and set a different background color for each subplot: red, blue, green, and yellow respectively. Which code snippet correctly applies these colors?

hard

A. colors = ['red', 'blue', 'green', 'yellow']
fig, axs = plt.subplots(2, 2)
for ax, color in zip(axs.flat, colors):
ax.set_facecolor(color)

B. colors = ['red', 'blue', 'green', 'yellow']
fig, axs = plt.subplots(2, 2)
for i in range(4):
axs[i].set_facecolor(colors[i])

C. colors = ['red', 'blue', 'green', 'yellow']
fig, axs = plt.subplots(2, 2)
for i, j in range(2):
axs[i, j].set_facecolor(colors[i+j])

D. colors = ['red', 'blue', 'green', 'yellow']
fig, axs = plt.subplots(2, 2)
for ax in axs:
ax.set_facecolor(colors)

Solution

1. Step 1: Understand axs structure and iteration

   With plt.subplots(2, 2), axs is a 2D array. Using axs.flat flattens it to 1D for easy iteration.

2. Step 2: Apply colors correctly

   Using zip(axs.flat, colors) pairs each subplot with a color. Calling ax.set_facecolor(color) sets background color individually.

3. Final Answer:

   Use axs.flat with zip and set_facecolor for each subplot -> Option A

4. Quick Check:

   Flatten axs and zip with colors = A [OK]

Hint: Use axs.flat to loop all subplots in order [OK]

Common Mistakes:

• Trying to index axs as 1D without flattening
• Using axs as 2D but wrong color indexing
• Passing full color list to set_facecolor