Figure size and DPI in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a figure with size 8 by 6 inches.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=[1])
plt.show()

Drag options to blanks, or click blank then click option'

A[8, 6]

B(8, 6)

C{8, 6}

D8, 6

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list or set instead of a tuple for figsize.

Not using any brackets around the numbers.

The figsize parameter expects a tuple with width and height in inches, so (8, 6) is correct.

2fill in blank

medium

Complete the code to set the DPI (dots per inch) of the figure to 150.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(dpi=[1])
plt.show()

Drag options to blanks, or click blank then click option'

A100

B72

C150

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Using a DPI value that is too low or default (like 72).

Confusing DPI with figure size.

The dpi parameter controls the resolution of the figure. Setting it to 150 increases the detail.

3fill in blank

hard

Fix the error in the code to create a figure with size 10 by 4 inches and DPI 120.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=[1], dpi=120)
plt.show()

Drag options to blanks, or click blank then click option'

A(10, 4)

B[10, 4]

C{10, 4}

D10, 4

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list or set instead of a tuple for figsize.

Not using any brackets around the numbers.

The figsize must be a tuple, so (10, 4) is correct. Lists or sets cause errors.

4fill in blank

hard

Fill both blanks to create a figure with size 12 by 8 inches and DPI 100.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=[1], dpi=[2])
plt.show()

Drag options to blanks, or click blank then click option'

A(12, 8)

B100

C150

D[12, 8]

Attempts:

3 left

💡 Hint

Common Mistakes

Using a list instead of a tuple for figsize.

Setting dpi to the wrong number.

Use a tuple (12, 8) for figsize and set dpi to 100 for the desired resolution.

5fill in blank

hard

Fill all three blanks to create a figure with size 5 by 5 inches, DPI 200, and save it as 'output.png'.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=[1], dpi=[2])
fig.savefig([3])
plt.show()

Drag options to blanks, or click blank then click option'

A(5, 5)

B200

C'output.png'

D'figure.png'

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the filename.

Using a list instead of a tuple for figsize.

Setting dpi to a wrong value.

Use (5, 5) for size, 200 for dpi, and save the figure as 'output.png'.

Practice

1. What does the figsize parameter control in a matplotlib figure?

easy

A. The physical size of the figure in inches

B. The color of the figure background

C. The resolution of the figure in dots per inch

D. The font size of the plot labels

Solution

1. Step 1: Understand the role of figsize

   The figsize parameter sets the width and height of the figure in inches.

2. Step 2: Differentiate from DPI

   DPI controls resolution, not size. Color and font size are unrelated to figsize.

3. Final Answer:

   The physical size of the figure in inches -> Option A

4. Quick Check:

   Figure size = physical dimensions [OK]

Hint: Remember: figsize = inches size, DPI = sharpness [OK]

Common Mistakes:

• Confusing DPI with figure size
• Thinking figsize controls resolution
• Mixing up color or font size with figsize

2. Which of the following is the correct way to create a matplotlib figure with size 8 inches wide and 4 inches tall?

easy

A. plt.figure(dpi=(8, 4))

B. plt.figure(size=(8, 4))

C. plt.figure(figsize=(8, 4))

D. plt.figure(shape=(8, 4))

Solution

1. Step 1: Recall correct parameter name

   The parameter to set figure size is figsize, which takes a tuple (width, height).

2. Step 2: Check syntax correctness

   Only plt.figure(figsize=(8, 4)) uses figsize correctly. Others use invalid parameter names.

3. Final Answer:

   plt.figure(figsize=(8, 4)) -> Option C

4. Quick Check:

   Use figsize=(width, height) [OK]

Hint: Use figsize=(width, height) tuple in plt.figure() [OK]

Common Mistakes:

• Using wrong parameter names like size or shape
• Passing DPI values instead of size
• Not using a tuple for figsize

3. What will be the DPI of the figure created by this code?

fig = plt.figure(figsize=(6, 3), dpi=150)

medium

A. 100

B. 150

C. 6

D. 3

Solution

1. Step 1: Identify the DPI parameter value

   The code explicitly sets dpi=150 when creating the figure.

2. Step 2: Understand DPI meaning

   DPI means dots per inch, so the figure resolution is 150 dots per inch.

3. Final Answer:

   150 -> Option B

4. Quick Check:

   DPI parameter sets resolution [OK]

Hint: DPI is set by dpi= value in plt.figure() [OK]

Common Mistakes:

• Confusing DPI with figure size
• Choosing width or height as DPI
• Assuming default DPI without checking code

4. Identify the error in this code snippet:

plt.figure(figsize=8, dpi=100)

medium

A. No error, code is correct

B. dpi must be a tuple, not an integer

C. plt.figure does not accept figsize parameter

D. figsize must be a tuple, not a single integer

Solution

1. Step 1: Check the type of figsize argument

   figsize expects a tuple (width, height), but 8 is a single integer.

2. Step 2: Verify dpi argument

   dpi accepts an integer, so dpi=100 is correct.

3. Final Answer:

   figsize must be a tuple, not a single integer -> Option D

4. Quick Check:

   figsize = (width, height) tuple [OK]

Hint: Always pass figsize as (width, height) tuple [OK]

Common Mistakes:

• Passing single int instead of tuple to figsize
• Thinking dpi needs a tuple
• Assuming figsize can be a single number

5. You want to save a plot image that is 10 inches wide and 5 inches tall with a resolution of 300 DPI. Which code snippet correctly creates and saves this figure?

hard

A. fig = plt.figure(figsize=(10, 5))
plt.plot([1, 2, 3])
fig.savefig('plot.png', dpi=300)

B. fig = plt.figure(figsize=(10, 5), dpi=100)
plt.plot([1, 2, 3])
fig.savefig('plot.png')

C. fig = plt.figure(dpi=300)
plt.plot([1, 2, 3])
fig.savefig('plot.png', figsize=(10, 5))

D. fig = plt.figure(figsize=10, dpi=300)
plt.plot([1, 2, 3])
fig.savefig('plot.png')

Solution

1. Step 1: Understand figure creation and saving

   Setting figsize in plt.figure() controls size on screen, but saving with specific DPI requires passing dpi to savefig().

2. Step 2: Analyze each option

   fig = plt.figure(figsize=(10, 5), dpi=100) plt.plot([1, 2, 3]) fig.savefig('plot.png') sets DPI in figure but saving uses default DPI, so output may differ. fig = plt.figure(figsize=(10, 5)) plt.plot([1, 2, 3]) fig.savefig('plot.png', dpi=300) sets size in figure and DPI in savefig, ensuring correct size and resolution. fig = plt.figure(dpi=300) plt.plot([1, 2, 3]) fig.savefig('plot.png', figsize=(10, 5)) wrongly passes figsize to savefig, which is invalid. fig = plt.figure(figsize=10, dpi=300) plt.plot([1, 2, 3]) fig.savefig('plot.png') passes single int to figsize, causing error.

3. Final Answer:

   fig = plt.figure(figsize=(10, 5)) plt.plot([1, 2, 3]) fig.savefig('plot.png', dpi=300) -> Option A

4. Quick Check:

   Set size in figure, DPI in savefig for correct output [OK]

Hint: Set figsize in figure, dpi in savefig to control size and resolution [OK]

Common Mistakes:

• Setting dpi only in figure but not in savefig
• Passing figsize to savefig instead of figure
• Using single int instead of tuple for figsize