Figure size for publication in Matplotlib - Step-by-Step Execution

Concept Flow - Figure size for publication

Start

↓

Set figure size with plt.figure(figsize=(w,h))

↓

Create plot elements (lines, labels)

↓

Adjust layout if needed

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Save figure with plt.savefig('file.png')

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End

This flow shows how to set the figure size for a plot, create the plot, and save it for publication.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
plt.figure(figsize=(6,4))
plt.plot([1,2,3],[4,5,6])
plt.title('Sample Plot')
plt.savefig('plot.png')
plt.show()

This code sets a 6x4 inch figure, plots a line, adds a title, saves the figure, and shows it.

Execution Table

Step	Action	Parameter/Value	Effect/Result
1	Import matplotlib.pyplot	-	plt module ready
2	Create figure	figsize=(6,4)	Figure size set to 6 inches wide, 4 inches tall
3	Plot data	x=[1,2,3], y=[4,5,6]	Line plotted on figure
4	Add title	'Sample Plot'	Title added to figure
5	Save figure	'plot.png'	Figure saved as 'plot.png' with set size
6	Show figure	-	Figure displayed on screen
7	End	-	Plotting complete

💡 All steps completed, figure saved and displayed with correct size

Variable Tracker

Variable	Start	After plt.figure()	After plt.plot()	After plt.title()	After plt.savefig()	Final
figsize	None	(6,4)	(6,4)	(6,4)	(6,4)	(6,4)
plot data	None	None	Line with points (1,4),(2,5),(3,6)	Same	Same	Same
title	None	None	None	'Sample Plot'	'Sample Plot'	'Sample Plot'
file saved	False	False	False	False	True	True

Key Moments - 3 Insights

Why do we use figsize=(6,4) in plt.figure()?

figsize sets the width and height in inches for the figure. This controls the size of the output image, important for publication quality. See execution_table step 2.

Does plt.savefig() save the figure with the size set by figsize?

Yes, plt.savefig() saves the figure exactly as sized by figsize. The saved image will have the dimensions in inches times the dpi. See execution_table step 5.

What happens if we don't call plt.figure(figsize=...) before plotting?

Matplotlib uses a default figure size (usually 6.4x4.8 inches). So the plot will be created but may not fit publication needs. See variable_tracker figsize start value.

Visual Quiz - 3 Questions

Look at the execution_table, what is the figure size set to at step 2?

A (8,6) inches

B (4,6) inches

C (6,4) inches

D (5,5) inches

💡 Hint

Check the 'Parameter/Value' column in execution_table row for step 2

At which step is the figure saved to a file?

A Step 5

B Step 3

C Step 6

D Step 4

💡 Hint

Look for 'Save figure' action in execution_table

If we change figsize to (8,6), how does variable_tracker change after plt.figure()?

A figsize remains None

B figsize changes to (8,6) after plt.figure()

C figsize changes to (6,4)

D figsize becomes (4,8)

💡 Hint

See how figsize updates after plt.figure() in variable_tracker

Concept Snapshot

plt.figure(figsize=(width,height)) sets figure size in inches
Create plots after setting size for publication quality
Save figure with plt.savefig('filename') to keep size
Default size used if figsize not set
Adjust size to fit journal or presentation needs

Full Transcript

This visual execution trace shows how to set the figure size for a matplotlib plot for publication. First, we import matplotlib.pyplot as plt. Then we create a figure with plt.figure(figsize=(6,4)) which sets the figure size to 6 inches wide and 4 inches tall. Next, we plot data points with plt.plot. We add a title using plt.title. Then we save the figure to a file with plt.savefig('plot.png'), which saves the image with the set size. Finally, we display the figure with plt.show. The variable tracker shows how figsize and other variables change step by step. Key moments clarify why figsize matters and how saving preserves size. The quiz tests understanding of figure size setting and saving steps.

Practice

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

easy

A. The font size of the labels

B. The width and height of the figure in inches

C. The color of the figure background

D. The style of the plot lines

Solution

1. Step 1: Understand the role of figsize

   The figsize parameter sets the size of the entire figure in inches, controlling width and height.

2. Step 2: Differentiate from other parameters

   Other parameters like color or font size do not affect figure size but appearance details.

3. Final Answer:

   The width and height of the figure in inches -> Option B

4. Quick Check:

   Figure size = width and height in inches [OK]

Hint: Remember figsize sets width and height in inches [OK]

Common Mistakes:

• Confusing figsize with color or font size
• Thinking figsize controls plot line style
• Assuming figsize is in pixels

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

easy

A. plt.figure(size=[8, 4])

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

C. plt.figure(width=8, height=4)

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

Solution

1. Step 1: Recall correct parameter name and type

   The parameter to set figure size is figsize and it expects a tuple (width, height).

2. Step 2: Check syntax correctness

   plt.figure(figsize=(8, 4)) uses figsize=(8, 4) which is correct syntax. Using size causes TypeError (unexpected keyword). Using width=8, height=4 also causes TypeError (no such parameters).

3. Final Answer:

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

4. Quick Check:

   Use figsize=(width, height) tuple [OK]

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

Common Mistakes:

• Using 'size' instead of 'figsize'
• Using separate width and height parameters
• Forgetting parentheses around figsize values

3. What will be the size of the figure in inches after running this code?

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

medium

A. 6 inches wide and 3 inches tall

B. 3 inches wide and 6 inches tall

C. Default size (usually 6.4 x 4.8 inches)

D. Cannot determine without dpi

Solution

1. Step 1: Identify figsize parameter values

   The code sets figsize=(6, 3), which means width=6 inches and height=3 inches.

2. Step 2: Understand effect on figure size

   This directly sets the figure size regardless of dpi, so the figure will be 6 inches wide and 3 inches tall.

3. Final Answer:

   6 inches wide and 3 inches tall -> Option A

4. Quick Check:

   figsize=(6, 3) means width=6, height=3 inches [OK]

Hint: figsize=(width, height) sets exact figure size in inches [OK]

Common Mistakes:

• Swapping width and height values
• Thinking dpi affects figsize dimensions
• Assuming default size if figsize is set

4. Identify the error in this code that tries to set figure size:

import matplotlib.pyplot as plt
plt.figure(figsize=8, 4)
plt.plot([1, 2], [3, 4])
plt.show()

medium

A. No error, code runs fine

B. plt.plot syntax is incorrect

C. figsize should be a tuple, not two separate arguments

D. plt.show() is missing parentheses

Solution

1. Step 1: Check figsize parameter usage

   The code uses figsize=8, 4 which passes two separate arguments instead of a single tuple.

2. Step 2: Understand correct figsize syntax

   Correct syntax requires a tuple: figsize=(8, 4). Without parentheses, it causes a TypeError.

3. Final Answer:

   figsize should be a tuple, not two separate arguments -> Option C

4. Quick Check:

   figsize=(width, height) needs parentheses [OK]

Hint: Always use parentheses for figsize tuple [OK]

Common Mistakes:

• Passing figsize values without parentheses
• Confusing plt.plot syntax errors
• Forgetting plt.show() parentheses (not the case here)

5. You want to create a publication-ready plot with a width of 7 inches and height of 5 inches. You also want to save it as a PNG file with 300 dpi resolution. Which code snippet correctly sets the figure size and saves the plot?

hard

A. plt.figure(figsize=(7, 5))
plt.plot(data)
plt.savefig('plot.png', dpi=300)

B. plt.figure(size=(7, 5))
plt.plot(data)
plt.savefig('plot.png', dpi=300)

C. plt.figure(figsize=[7, 5])
plt.plot(data)
plt.savefig('plot.png')

D. plt.figure(figsize=(7, 5))
plt.plot(data)
plt.save('plot.png', dpi=300)

Solution

1. Step 1: Set figure size correctly

   Use figsize=(7, 5) tuple in plt.figure() to set width and height in inches.

2. Step 2: Save figure with correct dpi and function

   Use plt.savefig('plot.png', dpi=300) to save with 300 dpi resolution. plt.figure(size=(7, 5)) plt.plot(data) plt.savefig('plot.png', dpi=300) uses wrong parameter size. plt.figure(figsize=[7, 5]) plt.plot(data) plt.savefig('plot.png') misses dpi. plt.figure(figsize=(7, 5)) plt.plot(data) plt.save('plot.png', dpi=300) uses wrong function plt.save.

3. Final Answer:

   plt.figure(figsize=(7, 5)) plt.plot(data) plt.savefig('plot.png', dpi=300) -> Option A

4. Quick Check:

   figsize tuple + savefig with dpi=300 [OK]

Hint: Use figsize tuple and savefig with dpi for publication [OK]

Common Mistakes:

• Using 'size' instead of 'figsize'
• Forgetting dpi in savefig for quality
• Using plt.save instead of plt.savefig