Axis limits (xlim, ylim) in Matplotlib - Step-by-Step Execution

Concept Flow - Axis limits (xlim, ylim)

Start Plot

↓

Plot Data Points

↓

Set x-axis limits with xlim

↓

Set y-axis limits with ylim

↓

Render Plot with new axis limits

↓

End

The plot starts with data points, then x and y axis limits are set, and finally the plot is rendered with these limits.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3, 4], [10, 20, 25, 30])
plt.xlim(1, 3)
plt.ylim(15, 28)
plt.show()

This code plots points and sets the x-axis limits from 1 to 3 and y-axis limits from 15 to 28.

Execution Table

Step	Action	xlim Values	ylim Values	Effect on Plot
1	Plot points (1,10), (2,20), (3,25), (4,30)	None	None	Plot shows all points with default axis limits
2	Set x-axis limits with plt.xlim(1, 3)	(1, 3)	None	X-axis now shows from 1 to 3, points outside hidden
3	Set y-axis limits with plt.ylim(15, 28)	(1, 3)	(15, 28)	Y-axis now shows from 15 to 28, points outside hidden
4	Render plot with new limits	(1, 3)	(15, 28)	Plot displays points within these axis ranges
5	End	(1, 3)	(15, 28)	Plot window closes or stays open depending on environment

💡 Plot rendering completes with xlim (1,3) and ylim (15,28) applied

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
xlim	None	(1, 3)	(1, 3)	(1, 3)
ylim	None	None	(15, 28)	(15, 28)

Key Moments - 3 Insights

Why do some points disappear after setting xlim and ylim?

Points outside the set axis limits are not shown because xlim and ylim restrict the visible range, as seen in execution_table steps 2 and 3.

What happens if xlim or ylim are set before plotting data?

Setting limits before plotting still works, but the plot will adjust to those limits when data is added, similar to steps 2 and 3 before step 1.

Can xlim and ylim be set to reverse the axis direction?

Yes, by setting the lower limit higher than the upper limit (e.g., xlim(3,1)), the axis direction reverses, changing the plot view.

Visual Quiz - 3 Questions

Look at the execution table, what are the xlim values after step 2?

A None

B (15, 28)

C (1, 3)

D (10, 30)

💡 Hint

Check the 'xlim Values' column at step 2 in the execution_table.

At which step do both xlim and ylim have values set?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look for the first row where both 'xlim Values' and 'ylim Values' columns are not None.

If you set plt.xlim(3,1), how would the plot change compared to step 2?

A X-axis direction reverses, showing values from 3 down to 1

B No change, same as (1,3)

C Plot will error and not show

D Y-axis limits also reverse automatically

💡 Hint

Recall axis limits can reverse axis direction if lower limit is greater than upper limit.

Concept Snapshot

plt.xlim(left, right) sets x-axis limits.
plt.ylim(bottom, top) sets y-axis limits.
Limits restrict visible data range.
Points outside limits are hidden.
Limits can reverse axis direction if reversed.

Full Transcript

This visual execution shows how matplotlib's xlim and ylim functions control the visible range of a plot's axes. First, data points are plotted. Then, xlim is set to (1,3), restricting the x-axis to show only values between 1 and 3. Next, ylim is set to (15,28), restricting the y-axis similarly. The plot updates to show only points within these ranges. Variables xlim and ylim change from None to their set tuples. Key moments clarify why points disappear outside limits and how axis direction can reverse. The quiz tests understanding of these steps and effects.

Practice

1. What does the function plt.xlim(0, 10) do in a matplotlib plot?

easy

A. Clears the current plot

B. Sets the y-axis limits from 0 to 10

C. Sets the x-axis limits from 0 to 10

D. Plots data points between 0 and 10 on x-axis

Solution

1. Step 1: Understand the function purpose

   plt.xlim() sets the limits of the x-axis in a plot.

2. Step 2: Analyze the arguments

   The arguments (0, 10) specify the minimum and maximum values for the x-axis.

3. Final Answer:

   Sets the x-axis limits from 0 to 10 -> Option C

4. Quick Check:

   plt.xlim(0, 10) = x-axis limits 0 to 10 [OK]

Hint: Remember xlim controls x-axis range, ylim controls y-axis [OK]

Common Mistakes:

• Confusing xlim with ylim
• Thinking it plots data points
• Assuming it clears the plot

2. Which of the following is the correct syntax to set y-axis limits from -5 to 5 in matplotlib?

easy

A. plt.ylim(-5, 5)

B. plt.xlim(-5, 5)

C. plt.axis(ymin=-5, ymax=5)

D. plt.set_ylim(-5, 5)

Solution

1. Step 1: Identify the function for y-axis limits

   The correct function to set y-axis limits is plt.ylim().

2. Step 2: Check the syntax

   The syntax plt.ylim(-5, 5) correctly sets the y-axis from -5 to 5.

3. Final Answer:

   plt.ylim(-5, 5) -> Option A

4. Quick Check:

   ylim(-5, 5) sets y-axis limits correctly [OK]

Hint: Use plt.ylim() for y-axis limits, not plt.xlim() [OK]

Common Mistakes:

• Using plt.xlim() for y-axis limits
• Using non-existent plt.set_ylim()
• Confusing plt.axis() parameters

3. What will be the x-axis limits after running this code?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3, 4])
plt.xlim(2, 3)
plt.show()

medium

A. [1, 4]

B. [2, 3]

C. [0, 1]

D. [3, 4]

Solution

1. Step 1: Understand the plot and xlim call

   The plot has x values 0 to 3 by default (index of list). The call plt.xlim(2, 3) sets the x-axis limits explicitly from 2 to 3.

2. Step 2: Confirm the axis limits

   Because of plt.xlim(2, 3), the x-axis will only show values between 2 and 3.

3. Final Answer:

   [2, 3] -> Option B

4. Quick Check:

   plt.xlim(2, 3) sets x-axis limits to [2, 3] [OK]

Hint: xlim sets exact x-axis range regardless of data [OK]

Common Mistakes:

• Assuming default axis limits remain
• Confusing data values with axis limits
• Ignoring that x-axis is index by default

4. Identify the error in this code snippet:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3])
plt.xlim(5, 1)
plt.show()

medium

A. plt.show() is missing parentheses

B. plt.plot() missing x values

C. plt.xlim() requires three arguments

D. xlim limits are reversed; min should be less than max

Solution

1. Step 1: Check the xlim arguments

   The call plt.xlim(5, 1) sets the lower limit to 5 and upper limit to 1, which is reversed.

2. Step 2: Understand axis limit rules

   Axis limits must have the minimum value first and maximum second. Reversed limits cause unexpected behavior or warnings.

3. Final Answer:

   xlim limits are reversed; min should be less than max -> Option D

4. Quick Check:

   Lower limit must be less than upper limit in xlim [OK]

Hint: Always put smaller number first in xlim and ylim [OK]

Common Mistakes:

• Reversing min and max values in limits
• Thinking xlim needs three arguments
• Ignoring function call syntax

5. You have a scatter plot with x values ranging from 0 to 100 and y values from 0 to 50. You want to zoom in on the region where x is between 20 and 40 and y is between 10 and 30. Which code correctly sets these axis limits?

hard

A. plt.xlim(20, 40)
plt.ylim(10, 30)

B. plt.xlim(10, 30)
plt.ylim(20, 40)

C. plt.xlim([10, 30])
plt.ylim([20, 40])

D. plt.axis([10, 30, 20, 40])

Solution

1. Step 1: Identify correct axis limits for x and y

   The question states x between 20 and 40, y between 10 and 30.

2. Step 2: Match limits to correct functions

   plt.xlim(20, 40) sets x-axis limits, plt.ylim(10, 30) sets y-axis limits correctly.

3. Final Answer:

   plt.xlim(20, 40) plt.ylim(10, 30) -> Option A

4. Quick Check:

   Use xlim for x-axis, ylim for y-axis limits [OK]

Hint: Match xlim to x-axis range, ylim to y-axis range [OK]

Common Mistakes:

• Swapping x and y limits
• Using list brackets in xlim/ylim
• Using plt.axis with wrong order