Figure creation with plt.figure in Matplotlib - Mini Project: Build & Apply

Figure creation with plt.figure

📖 Scenario: You are working on a simple data visualization project. You want to create a blank figure using matplotlib to prepare for adding plots later.

🎯 Goal: Create a blank figure using plt.figure with a specific size.

📋 What You'll Learn

Create a figure using plt.figure

Set the figure size to 6 inches wide and 4 inches tall

Store the figure in a variable called fig

Print the figure object to see its details

💡 Why This Matters

🌍 Real World

Creating figures is the first step in data visualization to prepare a canvas for charts and graphs.

💼 Career

Data scientists and analysts often create and customize figures to present data clearly and attractively.

1

Import matplotlib and create a blank figure

Import matplotlib.pyplot as plt. Then create a blank figure using plt.figure() and store it in a variable called fig.

Matplotlib

# Import matplotlib.pyplot as plt
# Create a blank figure and store it in fig
# Your code here

Hint

Use import matplotlib.pyplot as plt to import the plotting library.

Use fig = plt.figure() to create a blank figure.

2

Set the figure size

Modify the plt.figure() call to set the figure size to 6 inches wide and 4 inches tall using the figsize parameter.

Matplotlib

import matplotlib.pyplot as plt
# Create a figure with size 6 by 4 inches
fig = plt.figure(figsize=(6, 4))

Hint

Use figsize=(6, 4) inside plt.figure() to set the size.

3

Add a title to the figure

Use the fig.suptitle() method to add the title 'My Blank Figure' to the figure.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(6, 4))
# Add a title 'My Blank Figure' to the figure
fig.suptitle('My Blank Figure')

Hint

Use fig.suptitle('My Blank Figure') to add a title to the figure.

4

Print the figure object

Print the variable fig to display the figure object details.

Matplotlib

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(6, 4))
fig.suptitle('My Blank Figure')
# Print the figure object
print(fig)

Hint

Use print(fig) to show the figure object details.

Practice

1. What does the plt.figure() function do in matplotlib?

easy

A. Plots a line graph directly

B. Creates a new blank canvas for plotting graphs

C. Saves the current plot to a file

D. Displays the plot on the screen

Solution

1. Step 1: Understand the role of plt.figure()

   The plt.figure() function creates a new empty figure, which is like a blank canvas for drawing plots.

2. Step 2: Differentiate from other functions

   Functions like plt.plot() draw on the figure, plt.show() displays it, and plt.savefig() saves it. Only plt.figure() creates the blank space.

3. Final Answer:

   Creates a new blank canvas for plotting graphs -> Option B

4. Quick Check:

   plt.figure() = new blank canvas [OK]

Hint: Remember: figure = blank canvas for plots [OK]

Common Mistakes:

• Confusing plt.figure() with plt.plot()
• Thinking plt.figure() displays the plot
• Assuming plt.figure() saves the plot

2. Which of the following is the correct way to create a figure with size 8 inches wide and 6 inches tall using plt.figure()?

easy

A. plt.figure(size=(8, 6))

B. plt.figure(dimensions=(8, 6))

C. plt.figure(size=[8, 6])

D. plt.figure(figsize=(8, 6))

Solution

1. Step 1: Recall the correct parameter name

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

2. Step 2: Check the syntax of options

   Only plt.figure(figsize=(8, 6)) uses figsize=(8, 6) correctly. Others use wrong parameter names or data types.

3. Final Answer:

   plt.figure(figsize=(8, 6)) -> Option D

4. Quick Check:

   figsize=(width, height) = plt.figure(figsize=(8, 6)) [OK]

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

Common Mistakes:

• Using 'size' instead of 'figsize'
• Passing list instead of tuple
• Using wrong parameter names like 'dimensions'

3. What will be the output of this code?

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(4, 3), dpi=100)
print(fig.get_size_inches())
print(fig.dpi)

medium

A. [4 3]
100.0

B. [400 300]
100.0

C. [4. 3.]
100.0

D. [4.0 3.0]
10

Solution

1. Step 1: Understand figsize and dpi

   The figsize is in inches as a float array, so fig.get_size_inches() returns [4. 3.]. The dpi is dots per inch, set to 100.0.

2. Step 2: Check print outputs

   Printing fig.get_size_inches() shows floats with decimal points. Printing fig.dpi shows 100.0 as set.

3. Final Answer:

   [4. 3.] 100.0 -> Option C

4. Quick Check:

   figsize floats and dpi number = [4. 3.] and 100.0 [OK]

Hint: fig.get_size_inches() returns floats, dpi is float [OK]

Common Mistakes:

• Expecting integers instead of floats for size
• Confusing dpi value with size
• Misreading output format

4. Identify the error in this code snippet:

import matplotlib.pyplot as plt
fig = plt.figure(size=(5, 4))
plt.plot([1, 2, 3], [4, 5, 6])
plt.show()

medium

A. The parameter 'size' is invalid; should be 'figsize'

B. plt.plot() cannot be used after plt.figure()

C. plt.show() is missing parentheses

D. The lists in plt.plot() have different lengths

Solution

1. Step 1: Check parameter names in plt.figure()

   The correct parameter to set figure size is figsize, not size. Using size causes an error.

2. Step 2: Verify other parts of the code

   Using plt.plot() after plt.figure() is valid. plt.show() has parentheses. Lists have same length.

3. Final Answer:

   The parameter 'size' is invalid; should be 'figsize' -> Option A

4. Quick Check:

   Use figsize= not size= in plt.figure() [OK]

Hint: Use figsize=, not size=, to set figure size [OK]

Common Mistakes:

• Using 'size' instead of 'figsize'
• Thinking plt.plot() can't follow plt.figure()
• Forgetting parentheses in plt.show()

5. You want to create two separate plots in two separate windows. Which code correctly creates two figures and plots a simple line in each?

hard

A. fig1 = plt.figure(figsize=(4,3))
plt.plot([1,2,3],[4,5,6])
fig2 = plt.figure(figsize=(4,3))
plt.plot([1,2,3],[6,5,4])
plt.show()

B. plt.figure(figsize=(8,3))
plt.subplot(1,2,1)
plt.plot([1,2,3],[4,5,6])
plt.subplot(1,2,2)
plt.plot([1,2,3],[6,5,4])
plt.show()

C. fig = plt.figure(figsize=(8,3))
plt.plot([1,2,3],[4,5,6])
plt.plot([1,2,3],[6,5,4])
plt.show()

D. plt.figure(figsize=(4,3))
plt.plot([1,2,3],[4,5,6])
plt.figure(figsize=(4,3))
plt.plot([1,2,3],[6,5,4])

Solution

1. Step 1: Understand figure creation for multiple plots

   Creating two separate figures requires calling plt.figure() twice, each time creating a new blank canvas.

2. Step 2: Check code correctness

   fig1 = plt.figure(figsize=(4,3)) plt.plot([1,2,3],[4,5,6]) fig2 = plt.figure(figsize=(4,3)) plt.plot([1,2,3],[6,5,4]) plt.show() creates two figures with specified sizes and plots on each before showing. plt.figure(figsize=(8,3)) plt.subplot(1,2,1) plt.plot([1,2,3],[4,5,6]) plt.subplot(1,2,2) plt.plot([1,2,3],[6,5,4]) plt.show() uses subplots in one figure, not two figures. fig = plt.figure(figsize=(8,3)) plt.plot([1,2,3],[4,5,6]) plt.plot([1,2,3],[6,5,4]) plt.show() plots both lines on one figure. plt.figure(figsize=(4,3)) plt.plot([1,2,3],[4,5,6]) plt.figure(figsize=(4,3)) plt.plot([1,2,3],[6,5,4]) misses plt.show().

3. Final Answer:

   fig1 = plt.figure(figsize=(4,3)) plt.plot([1,2,3],[4,5,6]) fig2 = plt.figure(figsize=(4,3)) plt.plot([1,2,3],[6,5,4]) plt.show() -> Option A

4. Quick Check:

   Two plt.figure() calls = two separate plots [OK]

Hint: Call plt.figure() twice for separate plot windows [OK]

Common Mistakes:

• Using subplots instead of separate figures
• Plotting multiple lines on one figure expecting separate windows
• Forgetting plt.show() to display plots