Axis limits (xlim, ylim) in Matplotlib - Mini Project: Build & Apply

Axis limits (xlim, ylim)

📖 Scenario: You are analyzing the sales data of a small store over a week. You want to visualize the sales numbers clearly by setting the limits of the x-axis and y-axis on the graph.

🎯 Goal: Create a simple line plot of daily sales and set the x-axis limits to show only days 1 to 7 and the y-axis limits to show sales from 0 to 100.

📋 What You'll Learn

Create a list called days with values from 1 to 7 representing days of the week.

Create a list called sales with the exact sales numbers: 20, 35, 30, 50, 70, 65, 80.

Create two variables called x_min and x_max with values 1 and 7 respectively.

Create two variables called y_min and y_max with values 0 and 100 respectively.

Use plt.plot(days, sales) to plot the sales data.

Use plt.xlim(x_min, x_max) and plt.ylim(y_min, y_max) to set the axis limits.

Use plt.show() to display the plot.

💡 Why This Matters

🌍 Real World

Setting axis limits helps focus on important parts of data in graphs, making trends easier to see.

💼 Career

Data scientists and analysts often adjust axis limits to create clear and informative visualizations for reports and presentations.

1

Create the sales data lists

Create a list called days with values [1, 2, 3, 4, 5, 6, 7] and a list called sales with values [20, 35, 30, 50, 70, 65, 80].

Matplotlib

# Create the days and sales lists
# Your code here

Hint

Use square brackets to create lists. Put the exact numbers inside the lists separated by commas.

2

Set the axis limit variables

Create variables x_min and x_max with values 1 and 7 respectively. Also create variables y_min and y_max with values 0 and 100 respectively.

Matplotlib

days = [1, 2, 3, 4, 5, 6, 7]
sales = [20, 35, 30, 50, 70, 65, 80]
# Create x_min, x_max, y_min, y_max variables
# Your code here

Hint

Assign the numbers directly to the variable names using the equals sign.

3

Plot the sales data and set axis limits

Import matplotlib.pyplot as plt. Use plt.plot(days, sales) to plot the sales data. Then use plt.xlim(x_min, x_max) and plt.ylim(y_min, y_max) to set the x-axis and y-axis limits.

Matplotlib

days = [1, 2, 3, 4, 5, 6, 7]
sales = [20, 35, 30, 50, 70, 65, 80]
x_min = 1
x_max = 7
y_min = 0
y_max = 100
import matplotlib.pyplot as plt
# Plot the sales data and set axis limits
# Your code here

Hint

Use import matplotlib.pyplot as plt at the top. Then call plt.plot() with the two lists. Use plt.xlim() and plt.ylim() with the variables to set limits.

4

Display the plot

Use plt.show() to display the plot with the set axis limits.

Matplotlib

days = [1, 2, 3, 4, 5, 6, 7]
sales = [20, 35, 30, 50, 70, 65, 80]
x_min = 1
x_max = 7
y_min = 0
y_max = 100
import matplotlib.pyplot as plt
plt.plot(days, sales)
plt.xlim(x_min, x_max)
plt.ylim(y_min, y_max)
# Display the plot
# Your code here

Hint

Call plt.show() to open the graph window and see your plot.

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