Major and minor ticks in Matplotlib - Mini Project: Build & Apply

Major and Minor Ticks in Matplotlib

📖 Scenario: You are creating a simple line chart to show the sales trend over 10 days. To make the chart easier to read, you want to add both major and minor ticks on the x-axis.

🎯 Goal: Build a matplotlib line plot with major ticks every 2 days and minor ticks every day on the x-axis.

📋 What You'll Learn

Create a list called days with values from 1 to 10.

Create a list called sales with these exact values: 5, 7, 9, 6, 8, 10, 7, 9, 11, 8.

Create a plot with days on the x-axis and sales on the y-axis.

Set major ticks on the x-axis at every 2 days using MultipleLocator(2).

Set minor ticks on the x-axis at every 1 day using MultipleLocator(1).

Display the plot.

💡 Why This Matters

🌍 Real World

In real life, clear charts with well-placed ticks help people understand data trends easily, like sales over time or temperature changes.

💼 Career

Data scientists and analysts often customize plots to make reports and dashboards more readable and professional.

1

Create the data lists

Create a list called days with values from 1 to 10, and a list called sales with these exact values: 5, 7, 9, 6, 8, 10, 7, 9, 11, 8.

Matplotlib

# Create the days and sales lists
# Your code here

Hint

Use square brackets to create lists. For days, list numbers 1 through 10. For sales, use the exact numbers given.

2

Import matplotlib and set up the plot

Import matplotlib.pyplot as plt and import MultipleLocator from matplotlib.ticker. Then create a plot with days on the x-axis and sales on the y-axis using plt.plot(days, sales).

Matplotlib

days = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
sales = [5, 7, 9, 6, 8, 10, 7, 9, 11, 8]

# Import matplotlib.pyplot as plt and MultipleLocator
# Create a plot with days and sales
# Your code here

Hint

Use import matplotlib.pyplot as plt and from matplotlib.ticker import MultipleLocator. Then call plt.plot(days, sales) to create the line chart.

3

Add major and minor ticks on the x-axis

Use plt.gca() to get the current axes and assign it to ax. Then set major ticks on the x-axis every 2 days using ax.xaxis.set_major_locator(MultipleLocator(2)). Set minor ticks on the x-axis every 1 day using ax.xaxis.set_minor_locator(MultipleLocator(1)).

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator

days = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
sales = [5, 7, 9, 6, 8, 10, 7, 9, 11, 8]

plt.plot(days, sales)

# Get current axes as ax
# Set major ticks every 2 days
# Set minor ticks every 1 day
# Your code here

Hint

Use plt.gca() to get the axes. Then use ax.xaxis.set_major_locator(MultipleLocator(2)) and ax.xaxis.set_minor_locator(MultipleLocator(1)) to set ticks.

4

Display the plot

Use plt.show() to display the plot with major and minor ticks on the x-axis.

Matplotlib

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator

days = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
sales = [5, 7, 9, 6, 8, 10, 7, 9, 11, 8]

plt.plot(days, sales)

ax = plt.gca()
ax.xaxis.set_major_locator(MultipleLocator(2))
ax.xaxis.set_minor_locator(MultipleLocator(1))

# Display the plot
# Your code here

Hint

Call plt.show() to open the plot window and see the chart with ticks.

Practice

1. What is the main purpose of major ticks in a matplotlib plot?

easy

A. To change the color of the plot

B. To add grid lines to the plot

C. To label the plot title

D. To mark the main points on the axes

Solution

1. Step 1: Understand the role of major ticks

   Major ticks are the primary markers on the axes that show key values.

2. Step 2: Differentiate from other elements

   Grid lines and titles are different plot features, not related to major ticks.

3. Final Answer:

   To mark the main points on the axes -> Option D

4. Quick Check:

   Major ticks = main axis points [OK]

Hint: Major ticks show main axis points clearly [OK]

Common Mistakes:

• Confusing major ticks with grid lines
• Thinking major ticks change plot colors
• Mixing up ticks with plot titles

2. Which of the following is the correct way to set minor ticks on the x-axis using matplotlib?

easy

A. plt.minorticks_on()

B. plt.set_minor_ticks()

C. plt.minor_ticks()

D. plt.set_minor()

Solution

1. Step 1: Recall matplotlib minor ticks method

   The correct method to enable minor ticks is plt.minorticks_on().

2. Step 2: Check other options

   Other options are not valid matplotlib functions and will cause errors.

3. Final Answer:

   plt.minorticks_on() -> Option A

4. Quick Check:

   Enable minor ticks = plt.minorticks_on() [OK]

Hint: Use plt.minorticks_on() to enable minor ticks [OK]

Common Mistakes:

• Using non-existent functions like plt.set_minor_ticks()
• Confusing minor ticks enabling with setting labels
• Forgetting to call the function

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

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
fig, ax = plt.subplots()
ax.plot([1, 2, 3, 4])
ax.xaxis.set_major_locator(MultipleLocator(2))
ax.xaxis.set_minor_locator(MultipleLocator(0.5))
ax.minorticks_on()
plt.show()

medium

A. Major ticks every 2 units, minor ticks every 0.5 units on x-axis

B. Major ticks every 0.5 units, minor ticks every 2 units on x-axis

C. Only major ticks at 1 and 3, no minor ticks

D. Syntax error due to wrong locator usage

Solution

1. Step 1: Analyze major locator setting

   Major ticks are set every 2 units on the x-axis using MultipleLocator(2).

2. Step 2: Analyze minor locator setting

   Minor ticks are set every 0.5 units using MultipleLocator(0.5).

3. Final Answer:

   Major ticks every 2 units, minor ticks every 0.5 units on x-axis -> Option A

4. Quick Check:

   Major=2, Minor=0.5 units [OK]

Hint: Major locator sets big steps, minor locator sets small steps [OK]

Common Mistakes:

• Swapping major and minor locator values
• Assuming no minor ticks appear without plt.minorticks_on()
• Thinking locator causes syntax error

4. Identify the error in this code that tries to set minor ticks:

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
fig, ax = plt.subplots()
ax.plot([10, 20, 30])
ax.xaxis.set_minor_locator(MultipleLocator(1))
plt.minorticks_on()
plt.show()

medium

A. plt.minorticks_on() should be called on ax, not plt

B. No error, code runs fine

C. Missing plt.show() call

D. MultipleLocator cannot be used for minor ticks

Solution

1. Step 1: Check locator and import

   MultipleLocator is correctly used for minor ticks with proper import from matplotlib.ticker.

2. Step 2: Verify minorticks_on()

   plt.minorticks_on() works after plt.subplots() as it applies to the current axes object.

3. Final Answer:

   No error, code runs fine -> Option B

4. Quick Check:

   plt.minorticks_on() works with ax [OK]

Hint: plt.minorticks_on() works even with explicit axes objects [OK]

Common Mistakes:

• Not importing MultipleLocator from matplotlib.ticker
• Thinking MultipleLocator cannot be used for minor ticks
• Forgetting to call plt.show()

5. You want to create a plot with major ticks every 5 units and minor ticks every 1 unit on the y-axis only. Which code snippet correctly achieves this?

hard

A. ax.yaxis.set_major_locator(MultipleLocator(1))
ax.yaxis.set_minor_locator(MultipleLocator(5))
plt.minorticks_on()

B. ax.xaxis.set_major_locator(MultipleLocator(5))
ax.xaxis.set_minor_locator(MultipleLocator(1))
ax.minorticks_on()

C. ax.yaxis.set_major_locator(MultipleLocator(5))
ax.yaxis.set_minor_locator(MultipleLocator(1))
ax.minorticks_on()

D. ax.yaxis.set_major_locator(MultipleLocator(5))
ax.yaxis.set_minor_locator(MultipleLocator(1))
plt.minorticks_off()

Solution

1. Step 1: Set major and minor locators on y-axis

   Major ticks every 5 units and minor ticks every 1 unit require ax.yaxis.set_major_locator(MultipleLocator(5)) and ax.yaxis.set_minor_locator(MultipleLocator(1)).

2. Step 2: Enable minor ticks on the axes object

   Use ax.minorticks_on() to show minor ticks on the axes.

3. Final Answer:

   ax.yaxis.set_major_locator(MultipleLocator(5)) ax.yaxis.set_minor_locator(MultipleLocator(1)) ax.minorticks_on() -> Option C

4. Quick Check:

   Major=5, Minor=1 on y-axis with ax.minorticks_on() [OK]

Hint: Set locators on yaxis and call ax.minorticks_on() [OK]

Common Mistakes:

• Setting locators on x-axis instead of y-axis
• Calling plt.minorticks_on() instead of ax.minorticks_on()
• Swapping major and minor locator values