Figure size for publication in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of figure size in inches

What will be the output shape of the figure in inches after running this code?

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(6, 4))
print(fig.get_size_inches())

A [6. 4.]

B [4. 6.]

C [600 400]

D [0.6 0.4]

💡 Hint

The figsize parameter sets width and height in inches.

The figsize argument in plt.figure sets the width and height in inches. The get_size_inches() method returns a numpy array with these values.

❓ data_output

intermediate

Number of pixels in saved figure

If you save a figure with figsize=(5, 3) and dpi=100, how many pixels wide and tall will the saved image be?

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(5, 3), dpi=100)
width, height = fig.get_size_inches() * fig.dpi
print(int(width), int(height))

A 50 30

B 500 300

C 5 3

D 100 60

💡 Hint

Pixels = inches * dpi.

The figure size in inches multiplied by dpi gives the pixel dimensions of the saved image.

❓ visualization

advanced

Visual difference of figure sizes

Which option shows the correct code to create two side-by-side plots with different figure sizes for publication?

A

fig, axs = plt.subplots(2, 1)
fig.set_size_inches(10, 4)
axs[0].plot([1, 2, 3])
axs[1].plot([3, 2, 1])

B

fig1 = plt.figure(figsize=(5, 4))
fig2 = plt.figure(figsize=(10, 8))
plt.plot([1, 2, 3])

C

plt.figure(figsize=(10, 4))
plt.subplot(121)
plt.plot([1, 2, 3])
plt.figure(figsize=(5, 4))
plt.subplot(122)
plt.plot([3, 2, 1])

D

fig, axs = plt.subplots(1, 2, figsize=(10, 4))
axs[0].plot([1, 2, 3])
axs[1].plot([3, 2, 1])

💡 Hint

Use one figure with subplots and set figsize once.

Option D correctly creates one figure with two subplots side by side and sets the figure size once. Other options either create multiple figures or misuse subplot calls.

🧠 Conceptual

advanced

Effect of DPI on figure size and quality

How does increasing the dpi parameter affect the saved figure when figsize is fixed?

A The saved image has higher pixel dimensions and better quality but same physical size in inches.

B The saved image has larger physical size in inches but same pixel dimensions.

C The saved image has lower pixel dimensions and worse quality.

D The saved image size and quality do not change with dpi.

💡 Hint

Think about pixels per inch.

DPI means dots per inch. Increasing dpi increases pixels per inch, so the image has more pixels and better quality but the physical size in inches stays the same.

🔧 Debug

expert

Why does this saved figure have unexpected size?

Given this code, why is the saved figure smaller than expected? import matplotlib.pyplot as plt fig = plt.figure(figsize=(8, 6)) plt.plot([1, 2, 3]) fig.savefig('plot.png', dpi=50) Options:

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(8, 6))
plt.plot([1, 2, 3])
fig.savefig('plot.png', dpi=50)

A The plot command resets the figure size to default.

B The figsize is ignored when dpi is set in savefig.

C The dpi in savefig is lower than default, reducing pixel dimensions and making the image smaller.

D The file format PNG does not support large figure sizes.

💡 Hint

Check how dpi affects saved image size.

The dpi parameter in savefig controls the pixel density. Lower dpi means fewer pixels, so the saved image is smaller even if figsize is large.