Shared axes between subplots in Matplotlib - Step-by-Step Execution

Concept Flow - Shared axes between subplots

Create Figure

↓

Create Subplots with shared axes

↓

Plot data on each subplot

↓

Axes share limits and ticks

↓

Display combined plot

This flow shows creating a figure with multiple subplots that share x or y axes, so zooming or panning one affects the others.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
fig, axs = plt.subplots(2, 1, sharex=True)
axs[0].plot([1, 2, 3], [1, 4, 9])
axs[1].plot([1, 2, 3], [2, 3, 4])
plt.show()

Creates two vertical subplots sharing the x-axis and plots different data on each.

Execution Table

Step	Action	Result	Notes
1	Call plt.subplots(2,1, sharex=True)	Figure with 2 subplots created	Subplots share x-axis limits and ticks
2	Plot on axs[0]	Line plotted on top subplot	X-axis range set to [1,3], y-axis auto-scaled
3	Plot on axs[1]	Line plotted on bottom subplot	X-axis shared with top subplot
4	Display plot with plt.show()	Window opens showing 2 plots stacked vertically	X-axis ticks aligned and zoom/pan synced
5	User zooms x-axis on one subplot	Both subplots update x-axis range	Shared axis behavior confirmed
6	User zooms y-axis on one subplot	Only that subplot y-axis changes	Y-axis not shared, independent scaling
7	Execution ends	Plot window remains open until closed	End of script

💡 Plot window stays open until user closes it, script ends after plt.show()

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
fig	None	Figure object created	Same	Same	Same
axs	None	Array of 2 Axes objects	axs[0] has line plotted	axs[1] has line plotted	Same
x-axis limits	None	[1,3]	[1,3]	[1,3]	[1,3] shared
y-axis limits axs[0]	None	Auto	Auto scaled to [1,9]	Same	Same
y-axis limits axs[1]	None	Auto	Auto	Auto scaled to [2,4]	Same

Key Moments - 2 Insights

Why do both subplots update their x-axis when I zoom one but not the y-axis?

Because sharex=True links the x-axes of both subplots, so zooming one updates both. The y-axes are independent since sharey was not set, so only the zoomed subplot's y-axis changes. See execution_table rows 5 and 6.

What happens if I set sharey=True instead of sharex=True?

Then the y-axes will be linked and zooming or panning vertically on one subplot updates both y-axes. The x-axes remain independent. This is the opposite of the current example where only x is shared.

Visual Quiz - 3 Questions

Look at the execution table, what is the x-axis limit after plotting on both subplots?

A [1, 9]

B [0, 10]

C [1, 3]

D Auto-scaled independently

💡 Hint

Check the 'x-axis limits' row in variable_tracker after Step 3

At which step does the bottom subplot get its line plotted?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Action' column in execution_table for plotting on axs[1]

If sharex=False, how would the x-axis behavior change when zooming one subplot?

A Both subplots zoom together

B Only the zoomed subplot's x-axis changes

C Neither subplot zooms

D Both subplots zoom but y-axis stays fixed

💡 Hint

Recall that sharex=True links x-axes; without it, axes are independent

Concept Snapshot

Use plt.subplots(rows, cols, sharex=True/False, sharey=True/False) to create subplots that share axes.
Shared axes sync limits and ticks between subplots.
Zooming or panning one shared axis updates all linked subplots.
Unshared axes remain independent.
Common for comparing data with aligned scales.

Full Transcript

This lesson shows how to create multiple subplots in matplotlib that share axes. We start by creating a figure with two vertical subplots sharing the x-axis using plt.subplots(2,1,sharex=True). We plot different lines on each subplot. Because the x-axis is shared, zooming or panning the x-axis on one subplot updates the other automatically. The y-axes are independent, so zooming vertically affects only the subplot zoomed. The execution table traces each step: creating subplots, plotting lines, displaying the figure, and user interactions. The variable tracker shows how axes limits change. Key moments clarify why shared axes sync only the specified axis. The quiz tests understanding of axis limits, plotting steps, and behavior changes if sharing is disabled. This helps beginners see how shared axes work visually and practically.