Tick marks and tick labels in Matplotlib - Mini Project: Build & Apply

Tick marks and tick labels

📖 Scenario: You are creating a simple line chart to show the sales of a small shop over 5 days. You want to control the tick marks and labels on the x-axis to make the chart easy to read.

🎯 Goal: Build a matplotlib line chart with custom tick marks and tick labels on the x-axis.

📋 What You'll Learn

Create a list of sales numbers for 5 days.

Create a list of day names for the x-axis labels.

Plot the sales data as a line chart.

Set the x-axis tick marks to match the days.

Set the x-axis tick labels to the day names.

💡 Why This Matters

🌍 Real World

Customizing tick marks and labels helps make charts clearer and easier to understand in reports and presentations.

💼 Career

Data analysts and scientists often need to control chart details like tick marks to communicate data effectively.

1

Create sales data and day names

Create a list called sales with these values: 10, 15, 7, 12, 9. Create a list called days with these values: 'Mon', 'Tue', 'Wed', 'Thu', 'Fri'.

Matplotlib

# Create the sales list and the days list
# Your code here

Hint

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

2

Import matplotlib and prepare the plot

Import matplotlib.pyplot as plt. Use plt.figure() to create a new figure.

Matplotlib

sales = [10, 15, 7, 12, 9]
days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri']
# Import matplotlib.pyplot as plt
# Create a new figure with plt.figure()
# Your code here

Hint

Use import matplotlib.pyplot as plt to import. Then call plt.figure() to start a new plot.

3

Plot sales and set x-axis ticks and labels

Use plt.plot(sales) to plot the sales data. Use plt.xticks() to set the tick marks at positions 0, 1, 2, 3, 4 and the tick labels to the days list.

Matplotlib

import matplotlib.pyplot as plt

sales = [10, 15, 7, 12, 9]
days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri']

plt.figure()
# Plot the sales data
# Set x-axis tick marks at 0,1,2,3,4
# Set x-axis tick labels to days
# Your code here

Hint

Use plt.plot(sales) to draw the line. Use plt.xticks() with two arguments: a list of positions and a list of labels.

4

Display the plot

Use plt.show() to display the plot with the custom tick marks and labels.

Matplotlib

import matplotlib.pyplot as plt

sales = [10, 15, 7, 12, 9]
days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri']

plt.figure()
plt.plot(sales)
plt.xticks([0, 1, 2, 3, 4], days)
# Display the plot
# Your code here

Hint

Call plt.show() to open the plot window.

Practice

1. What do tick marks on a matplotlib graph represent?

easy

A. The color of the graph lines

B. Positions on the axis where values are shown

C. The title of the graph

D. The size of the graph figure

Solution

1. Step 1: Understand the role of tick marks

   Tick marks are small marks along the axis that show where specific values lie.

2. Step 2: Identify what tick marks indicate on a graph

   They help us see the scale and exact positions of data points on the axis.

3. Final Answer:

   Positions on the axis where values are shown -> Option B

4. Quick Check:

   Tick marks = axis positions [OK]

Hint: Tick marks show value positions on axes [OK]

Common Mistakes:

• Confusing tick marks with graph title
• Thinking tick marks control graph color
• Mixing tick marks with figure size

2. Which of the following is the correct way to set custom tick labels on the x-axis in matplotlib?

easy

A. plt.ticklabels([1, 2, 3], ['A', 'B', 'C'])

B. plt.set_xticks(['A', 'B', 'C'])

C. plt.xticks([1, 2, 3], ['A', 'B', 'C'])

D. plt.xlabels([1, 2, 3], ['A', 'B', 'C'])

Solution

1. Step 1: Recall the matplotlib function for setting ticks and labels

   The function plt.xticks() sets both tick positions and their labels on the x-axis.

2. Step 2: Check the syntax of plt.xticks()

   It takes two arguments: a list of positions and a list of labels, like plt.xticks([1, 2, 3], ['A', 'B', 'C']).

3. Final Answer:

   plt.xticks([1, 2, 3], ['A', 'B', 'C']) -> Option C

4. Quick Check:

   Custom x-axis labels use plt.xticks() [OK]

Hint: Use plt.xticks(positions, labels) to set x-axis labels [OK]

Common Mistakes:

• Using non-existent functions like plt.ticklabels
• Confusing tick positions with labels
• Using plt.set_xticks() without labels

3. What will be the output of this code snippet?

import matplotlib.pyplot as plt
plt.plot([10, 20, 30])
plt.xticks([0, 1, 2], ['Low', 'Medium', 'High'])
plt.show()

medium

A. A scatter plot with labels 'Low', 'Medium', 'High'

B. A line plot with default numeric x-axis labels 0, 1, 2

C. An error because plt.xticks() is used incorrectly

D. A line plot with x-axis labels 'Low', 'Medium', 'High' at positions 0, 1, 2

Solution

1. Step 1: Understand the plot and xticks usage

   The plot shows points at y-values 10, 20, 30 with default x positions 0, 1, 2.

2. Step 2: Analyze plt.xticks() effect

   plt.xticks([0, 1, 2], ['Low', 'Medium', 'High']) replaces x-axis tick labels at positions 0,1,2 with the given strings.

3. Final Answer:

   A line plot with x-axis labels 'Low', 'Medium', 'High' at positions 0, 1, 2 -> Option D

4. Quick Check:

   xticks sets custom labels at given positions [OK]

Hint: xticks changes labels, not plot type [OK]

Common Mistakes:

• Thinking xticks changes plot type
• Expecting numeric labels after setting strings
• Confusing positions and labels order

4. Identify the error in this code that tries to rotate x-axis tick labels:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3])
plt.xticks(rotation=45)
plt.show()

medium

A. No error; code runs correctly

B. plt.xticks() needs positions and labels to rotate

C. plt.xticks() must be called before plt.plot()

D. rotation argument is not valid in plt.xticks()

Solution

1. Step 1: Check plt.xticks() usage with rotation

   plt.xticks() can be called with rotation parameter alone to rotate existing tick labels.

2. Step 2: Confirm code correctness

   The code plots points and rotates x-axis labels by 45 degrees without needing to specify positions or labels.

3. Final Answer:

   No error; code runs correctly -> Option A

4. Quick Check:

   Rotation works with plt.xticks(rotation=angle) [OK]

Hint: Rotation works without specifying labels [OK]

Common Mistakes:

• Thinking positions are required to rotate labels
• Believing rotation is invalid argument
• Assuming plot order affects xticks rotation

5. You have a bar chart with 5 bars. You want to set custom labels ['A', 'B', 'C', 'D', 'E'] on the x-axis and rotate them 60 degrees for better readability. Which code snippet correctly does this?

hard

A. plt.xticks(range(5), ['A', 'B', 'C', 'D', 'E'], rotation=60)

B. plt.xticks(['A', 'B', 'C', 'D', 'E'], range(5), rotation=60)

C. plt.xticks(rotation=60)
plt.xticks(range(5), ['A', 'B', 'C', 'D', 'E'])

D. plt.xticks(range(5), ['A', 'B', 'C', 'D', 'E'])
plt.xticks(rotation=60)

Solution

1. Step 1: Understand plt.xticks() parameters

   plt.xticks() takes positions as first argument, labels as second, and rotation as a keyword argument.

2. Step 2: Check which option sets labels and rotation together

   plt.xticks(range(5), ['A', 'B', 'C', 'D', 'E'], rotation=60) correctly passes positions, labels, and rotation in one call.

3. Step 3: Analyze other options

   plt.xticks(['A', 'B', 'C', 'D', 'E'], range(5), rotation=60) swaps positions and labels incorrectly; A and C call plt.xticks() twice, which may override settings.

4. Final Answer:

   plt.xticks(range(5), ['A', 'B', 'C', 'D', 'E'], rotation=60) -> Option A

5. Quick Check:

   Set labels and rotation in one plt.xticks() call [OK]

Hint: Use plt.xticks(positions, labels, rotation=angle) [OK]

Common Mistakes:

• Swapping positions and labels arguments
• Calling plt.xticks() twice causing override
• Forgetting to pass rotation argument