Title and axis labels in Matplotlib - Mini Project: Build & Apply

Title and axis labels

📖 Scenario: You are analyzing sales data for a small store. You want to create a simple line chart to show how sales changed over a week.

🎯 Goal: Create a line chart using matplotlib with a title and labels for the x-axis and y-axis to clearly explain the chart.

📋 What You'll Learn

Create a list called days with the days of the week from Monday to Sunday.

Create a list called sales with the sales numbers for each day: 150, 200, 170, 220, 180, 190, 210.

Use matplotlib.pyplot to plot the sales data as a line chart.

Add a chart title using plt.title() with the text 'Weekly Sales'.

Add an x-axis label using plt.xlabel() with the text 'Day of the Week'.

Add a y-axis label using plt.ylabel() with the text 'Sales (units)'.

Display the chart using plt.show().

💡 Why This Matters

🌍 Real World

Adding titles and axis labels helps anyone looking at your charts understand what the data means quickly.

💼 Career

Data scientists and analysts always label their charts clearly to communicate insights effectively to others.

1

Create the sales data lists

Create a list called days with these exact values: 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'. Then create a list called sales with these exact values: 150, 200, 170, 220, 180, 190, 210.

Matplotlib

# Create the days and sales lists
# Your code here

Hint

Use square brackets to create lists. Separate items with commas.

2

Import matplotlib and prepare to plot

Import matplotlib.pyplot as plt. This will let you create charts easily.

Matplotlib

days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
sales = [150, 200, 170, 220, 180, 190, 210]

# Import matplotlib.pyplot as plt
# Your code here

Hint

Use the import statement to bring in matplotlib.pyplot and rename it as plt.

3

Plot the sales data with title and axis labels

Use plt.plot(days, sales) to create a line chart. Then add a title with plt.title('Weekly Sales'). Add an x-axis label with plt.xlabel('Day of the Week') and a y-axis label with plt.ylabel('Sales (units)').

Matplotlib

import matplotlib.pyplot as plt

days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
sales = [150, 200, 170, 220, 180, 190, 210]

# Plot the sales data
# Add title and axis labels
# Your code here

Hint

Use plt.plot() to draw the line. Use plt.title(), plt.xlabel(), and plt.ylabel() to add text.

4

Display the chart

Use plt.show() to display the chart with the title and axis labels.

Matplotlib

import matplotlib.pyplot as plt

days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
sales = [150, 200, 170, 220, 180, 190, 210]

plt.plot(days, sales)
plt.title('Weekly Sales')
plt.xlabel('Day of the Week')
plt.ylabel('Sales (units)')

# Display the chart
# Your code here

Hint

Call plt.show() to see the chart window pop up.

Practice

1. Which matplotlib function is used to add a title to a plot?

easy

A. plt.axis()

B. plt.label()

C. plt.legend()

D. plt.title()

Solution

1. Step 1: Understand the purpose of plt.title()

   This function adds a title text at the top of the plot, describing what the plot shows.

2. Step 2: Compare with other functions

   plt.label() does not exist, plt.legend() adds a legend, and plt.axis() controls axis limits, so they don't add a title.

3. Final Answer:

   plt.title() -> Option D

4. Quick Check:

   Title function = plt.title() [OK]

Hint: Title is always set with plt.title() [OK]

Common Mistakes:

• Using plt.label() instead of plt.title()
• Confusing legend with title
• Trying plt.axis() for title

2. Which of the following is the correct syntax to label the x-axis as 'Time (seconds)' in matplotlib?

easy

A. plt.xlabel('Time (seconds)')

B. plt.xaxis('Time (seconds)')

C. plt.label('x', 'Time (seconds)')

D. plt.axislabel('Time (seconds)')

Solution

1. Step 1: Recall the function to label x-axis

   The correct function is plt.xlabel() which takes the label text as argument.

2. Step 2: Check other options for syntax errors

   plt.xaxis(), plt.label(), and plt.axislabel() are not valid matplotlib functions for axis labeling.

3. Final Answer:

   plt.xlabel('Time (seconds)') -> Option A

4. Quick Check:

   X-axis label = plt.xlabel() [OK]

Hint: Use plt.xlabel() for x-axis label text [OK]

Common Mistakes:

• Using plt.xaxis() which doesn't exist
• Trying plt.label() for axis
• Confusing axis limits with labels

3. What will be the output of the following code?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.title('Sales Over Time')
plt.xlabel('Month')
plt.ylabel('Sales')
plt.show()

medium

A. A plot with title but no axis labels

B. A plot with no title and no axis labels

C. A plot with title 'Sales Over Time', x-axis labeled 'Month', y-axis labeled 'Sales'

D. A plot with axis labels but no title

Solution

1. Step 1: Analyze the code lines for title and labels

   The code uses plt.title('Sales Over Time') to add a title, plt.xlabel('Month') for x-axis label, and plt.ylabel('Sales') for y-axis label.

2. Step 2: Understand the plot display

   The plot will show the line graph with all these labels visible as specified.

3. Final Answer:

   A plot with title 'Sales Over Time', x-axis labeled 'Month', y-axis labeled 'Sales' -> Option C

4. Quick Check:

   Title and axis labels set correctly [OK]

Hint: Check all label functions called before plt.show() [OK]

Common Mistakes:

• Forgetting plt.title() call
• Mixing up xlabel and ylabel
• Not calling plt.show() to display

4. Identify the error in this code snippet that tries to add a title and axis labels:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1])
plt.title = 'My Plot'
plt.xlabel('X Axis')
plt.ylabel('Y Axis')
plt.show()

medium

A. Using assignment operator '=' instead of function call for plt.title

B. Missing plt.show() call

C. Incorrect order of xlabel and ylabel calls

D. plt.plot() arguments are invalid

Solution

1. Step 1: Check how title is set

   The code uses plt.title = 'My Plot' which assigns a string to the function name, overwriting it instead of calling it.

2. Step 2: Understand correct usage

   The correct way is to call the function: plt.title('My Plot') to set the title.

3. Final Answer:

   Using assignment operator '=' instead of function call for plt.title -> Option A

4. Quick Check:

   Title must be set by calling plt.title() [OK]

Hint: Use parentheses () to call plt.title() function [OK]

Common Mistakes:

• Assigning string to plt.title instead of calling
• Forgetting plt.show()
• Swapping xlabel and ylabel calls

5. You want to create a plot with the title 'Temperature Trends', x-axis labeled 'Day', and y-axis labeled 'Temperature (°C)'. Which code snippet correctly achieves this?

hard

A. plt.plot(days, temps)
plt.title = 'Temperature Trends'
plt.xlabel = 'Day'
plt.ylabel = 'Temperature (°C)'
plt.show()

B. plt.plot(days, temps)
plt.title('Temperature Trends')
plt.xlabel('Day')
plt.ylabel('Temperature (°C)')
plt.show()

C. plt.plot(days, temps)
plt.set_title('Temperature Trends')
plt.set_xlabel('Day')
plt.set_ylabel('Temperature (°C)')
plt.show()

D. plt.plot(days, temps)
plt.title('Temperature Trends')
plt.xaxis('Day')
plt.yaxis('Temperature (°C)')
plt.show()

Solution

1. Step 1: Verify correct function calls for title and labels

   plt.plot(days, temps) plt.title('Temperature Trends') plt.xlabel('Day') plt.ylabel('Temperature (°C)') plt.show() uses plt.title(), plt.xlabel(), and plt.ylabel() correctly with parentheses and proper arguments.

2. Step 2: Check other options for errors

   plt.plot(days, temps) plt.title = 'Temperature Trends' plt.xlabel = 'Day' plt.ylabel = 'Temperature (°C)' plt.show() incorrectly assigns strings to functions, plt.plot(days, temps) plt.set_title('Temperature Trends') plt.set_xlabel('Day') plt.set_ylabel('Temperature (°C)') plt.show() uses non-existent set_title functions, and plt.plot(days, temps) plt.title('Temperature Trends') plt.xaxis('Day') plt.yaxis('Temperature (°C)') plt.show() uses invalid xaxis and yaxis functions.

3. Final Answer:

   plt.plot(days, temps) plt.title('Temperature Trends') plt.xlabel('Day') plt.ylabel('Temperature (°C)') plt.show() -> Option B

4. Quick Check:

   Use plt.title(), plt.xlabel(), plt.ylabel() with parentheses [OK]

Hint: Always call plt.title(), plt.xlabel(), plt.ylabel() as functions [OK]

Common Mistakes:

• Assigning labels instead of calling functions
• Using non-existent set_title() methods
• Using plt.xaxis() instead of plt.xlabel()