Unequal subplot sizes in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of unequal subplot sizes with gridspec

What is the output of this code snippet that creates two subplots with different widths using matplotlib's gridspec?

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec

fig = plt.figure()
gs = GridSpec(1, 2, width_ratios=[3, 1])
ax1 = fig.add_subplot(gs[0])
ax2 = fig.add_subplot(gs[1])
ax1.plot([1, 2, 3], [1, 4, 9])
ax2.plot([1, 2, 3], [1, 2, 3])
plt.show()
print((ax1.get_position().width > ax2.get_position().width))

A Raises ValueError

B True

C Raises AttributeError

D False

💡 Hint

Check the width_ratios parameter and how it affects subplot widths.

The width_ratios=[3,1] means the first subplot is three times wider than the second. So ax1's width is greater than ax2's, making the print output True.

❓ data_output

intermediate

Number of axes created with unequal subplot sizes

How many axes objects are created by this code that uses GridSpec with unequal height ratios?

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec

fig = plt.figure()
gs = GridSpec(2, 1, height_ratios=[2, 1])
ax1 = fig.add_subplot(gs[0])
ax2 = fig.add_subplot(gs[1])
plt.close(fig)
print(len(fig.axes))

A 0

B 1

C 2

D Raises IndexError

💡 Hint

Count how many subplots are added to the figure.

Two subplots are created and added to the figure, so fig.axes contains two axes objects.

🔧 Debug

advanced

Identify the error in subplot size code

What error does this code raise when trying to create subplots with unequal sizes using gridspec?

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec

fig = plt.figure()
gs = GridSpec(1, 2, width_ratios=[2])
ax1 = fig.add_subplot(gs[0])
ax2 = fig.add_subplot(gs[1])
plt.show()

A ValueError: width_ratios must have length 2

B IndexError: index out of range

C TypeError: unsupported operand type(s)

D No error, plots successfully

💡 Hint

Check the length of width_ratios compared to number of columns.

width_ratios must match the number of columns (2), but only one value is given, causing a ValueError.

❓ visualization

advanced

Visual difference in subplot heights

Which option produces a figure with two vertically stacked subplots where the top subplot is twice as tall as the bottom one?

A

gs = GridSpec(2, 1, height_ratios=[1, 2])
fig.add_subplot(gs[0])
fig.add_subplot(gs[1])

B

gs = GridSpec(1, 2, width_ratios=[2, 1])
fig.add_subplot(gs[0])
fig.add_subplot(gs[1])

C

gs = GridSpec(1, 2, width_ratios=[1, 2])
fig.add_subplot(gs[0])
fig.add_subplot(gs[1])

D

gs = GridSpec(2, 1, height_ratios=[2, 1])
fig.add_subplot(gs[0])
fig.add_subplot(gs[1])

💡 Hint

Height ratios control vertical size; width ratios control horizontal size.

Option D sets height_ratios=[2,1] for two rows, making the top subplot twice as tall as the bottom.

🚀 Application

expert

Create a complex layout with unequal subplot sizes

You want to create a figure with 3 subplots arranged in 2 rows and 2 columns. The top row has one subplot spanning both columns, and the bottom row has two subplots with widths ratio 3:1. Which code snippet achieves this layout?

A

gs = GridSpec(2, 2, width_ratios=[3, 1])
ax1 = fig.add_subplot(gs[0, :])
ax2 = fig.add_subplot(gs[1, 0])
ax3 = fig.add_subplot(gs[1, 1])

B

gs = GridSpec(2, 2, width_ratios=[1, 3])
ax1 = fig.add_subplot(gs[0, :])
ax2 = fig.add_subplot(gs[1, 0])
ax3 = fig.add_subplot(gs[1, 1])

C

gs = GridSpec(2, 2, height_ratios=[1, 2])
ax1 = fig.add_subplot(gs[0, :])
ax2 = fig.add_subplot(gs[1, 0])
ax3 = fig.add_subplot(gs[1, 1])

D

gs = GridSpec(2, 2)
ax1 = fig.add_subplot(gs[0, :])
ax2 = fig.add_subplot(gs[1, 0])
ax3 = fig.add_subplot(gs[1, 1])

💡 Hint

Use width_ratios to control bottom row widths and slice for top row spanning both columns.

Option A uses width_ratios=[3,1] to set bottom row widths and gs[0, :] to span top subplot across both columns.

Practice

1. What is the main advantage of using unequal subplot sizes in matplotlib?

easy

A. To automatically adjust colors of the plots

B. To make all charts the same size for uniformity

C. To highlight important charts by giving them more space

D. To reduce the total number of charts displayed

Solution

1. Step 1: Understand subplot size purpose

   Unequal subplot sizes allow some plots to be larger, drawing more attention.

2. Step 2: Compare options

   Only To highlight important charts by giving them more space mentions highlighting important charts by size, which is the main advantage.

3. Final Answer:

   To highlight important charts by giving them more space -> Option C

4. Quick Check:

   Unequal sizes highlight key charts [OK]

Hint: Unequal sizes = emphasize important plots [OK]

Common Mistakes:

• Thinking all subplots must be equal size
• Confusing size with color or number of plots
• Assuming unequal sizes reduce charts

2. Which of the following is the correct way to create subplots with unequal sizes using gridspec_kw in plt.subplots()?

easy

A. plt.subplots(1, 2, gridspec_kw={'width_ratios': [2, 1]})

B. plt.subplots(2, 1, gridspec_kw={'height_ratios': [1, 2]})

C. plt.subplots(1, 2, gridspec_kw={'height_ratios': [2, 1]})

D. plt.subplots(2, 1, gridspec_kw={'width_ratios': [1, 2]})

Solution

1. Step 1: Identify correct parameter for horizontal subplots

   For 1 row and 2 columns, use 'width_ratios' to set horizontal size ratios.

2. Step 2: Match ratios to subplot layout

   plt.subplots(1, 2, gridspec_kw={'width_ratios': [2, 1]}) uses 1 row, 2 columns with width_ratios, which is correct syntax.

3. Final Answer:

   plt.subplots(1, 2, gridspec_kw={'width_ratios': [2, 1]}) -> Option A

4. Quick Check:

   Width ratios for columns = plt.subplots(1, 2, gridspec_kw={'width_ratios': [2, 1]}) [OK]

Hint: Use width_ratios for columns, height_ratios for rows [OK]

Common Mistakes:

• Mixing width_ratios with rows instead of columns
• Using height_ratios for horizontal layout
• Wrong number of rows and columns in function

3. What will be the width ratio of the two subplots created by this code?

fig, axs = plt.subplots(1, 2, gridspec_kw={'width_ratios': [3, 1]})

medium

A. Both subplots have equal width

B. The subplots have random widths

C. The second subplot is 3 times wider than the first

D. The first subplot is 3 times wider than the second

Solution

1. Step 1: Understand width_ratios parameter

   The list [3, 1] means the first subplot width is 3 units, second is 1 unit.

2. Step 2: Interpret ratio meaning

   This means the first subplot is 3 times wider than the second subplot.

3. Final Answer:

   The first subplot is 3 times wider than the second -> Option D

4. Quick Check:

   Width ratio 3:1 means first is 3x wider [OK]

Hint: Ratio list directly shows relative sizes [OK]

Common Mistakes:

• Assuming equal widths despite ratios
• Reversing which subplot is wider
• Ignoring the ratio values

4. Identify the error in this code that tries to create unequal subplot sizes:

fig, axs = plt.subplots(2, 1, gridspec_kw={'width_ratios': [1, 2]})

medium

A. Incorrect number of subplots specified

B. Using width_ratios for vertical subplots instead of height_ratios

C. Missing plt.show() to display plots

D. width_ratios list length does not match subplot count

Solution

1. Step 1: Check subplot layout

   2 rows and 1 column means vertical stacking of subplots.

2. Step 2: Verify correct ratio parameter

   For vertical layout, use 'height_ratios', not 'width_ratios'.

3. Final Answer:

   Using width_ratios for vertical subplots instead of height_ratios -> Option B

4. Quick Check:

   Vertical layout needs height_ratios [OK]

Hint: Use height_ratios for rows, width_ratios for columns [OK]

Common Mistakes:

• Confusing width_ratios and height_ratios
• Ignoring subplot grid shape
• Assuming plt.show() affects subplot sizes

5. You want to create a figure with 3 subplots in one row where the middle subplot is twice as wide as the others. Which code correctly achieves this?

hard

A. plt.subplots(1, 3, gridspec_kw={'width_ratios': [1, 2, 1]})

B. plt.subplots(3, 1, gridspec_kw={'height_ratios': [1, 2, 1]})

C. plt.subplots(1, 3, gridspec_kw={'height_ratios': [1, 2, 1]})

D. plt.subplots(3, 1, gridspec_kw={'width_ratios': [1, 2, 1]})

Solution

1. Step 1: Determine subplot layout

   One row and three columns means horizontal layout.

2. Step 2: Choose correct ratio parameter

   For horizontal layout, use 'width_ratios' to set widths.

3. Step 3: Set ratios to make middle subplot twice as wide

   Use [1, 2, 1] so middle subplot is twice the width of others.

4. Final Answer:

   plt.subplots(1, 3, gridspec_kw={'width_ratios': [1, 2, 1]}) -> Option A

5. Quick Check:

   Horizontal layout with width_ratios = plt.subplots(1, 3, gridspec_kw={'width_ratios': [1, 2, 1]}) [OK]

Hint: Middle subplot twice wide = width_ratios [1, 2, 1] [OK]

Common Mistakes:

• Using height_ratios for horizontal layout
• Setting wrong number of rows and columns
• Reversing ratio order