What is Matplotlib - Practice Questions & Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of Matplotlib in Data Science

What is the main purpose of Matplotlib in data science?

A To clean and preprocess raw data before analysis

B To perform statistical tests on data

C To store large datasets efficiently on disk

D To create visual representations like charts and graphs from data

💡 Hint

Think about how you can show data in pictures to understand it better.

Matplotlib is a library used to draw charts and graphs, helping us see patterns in data.

❓ Predict Output

intermediate

Output of Simple Matplotlib Code

What will this code display when run?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.show()

A No output, the code will raise an error

B A bar chart with bars at heights 1, 2, and 3

C A line graph connecting points (1,4), (2,5), and (3,6)

D A scatter plot with points at (4,1), (5,2), and (6,3)

💡 Hint

plt.plot draws lines between points given by x and y lists.

The plt.plot function draws a line graph connecting the points defined by the x and y lists.

❓ data_output

advanced

Data Points in a Matplotlib Scatter Plot

How many points will be shown in the scatter plot from this code?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 25, 30]
plt.scatter(x, y)
plt.show()

A 4 points

B 3 points

C 1 point

D No points, code raises an error

💡 Hint

Each pair of x and y values creates one point.

The scatter plot shows one point for each pair of x and y values, so 4 points total.

❓ visualization

advanced

Effect of Changing Line Style in Matplotlib

What visual change happens if you add linestyle='--' to plt.plot?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6], linestyle='--')
plt.show()

A The line becomes dashed instead of solid

B The line color changes to red

C The plot shows points without connecting lines

D The plot raises a syntax error

💡 Hint

linestyle controls how the line looks between points.

Setting linestyle='--' changes the line to a dashed style.

🔧 Debug

expert

Error Raised by Incorrect Matplotlib Import

What error will this code raise?

Matplotlib

import matplotlib
matplotlib.plot([1, 2, 3], [4, 5, 6])
matplotlib.show()

A SyntaxError: invalid syntax

B AttributeError: module 'matplotlib' has no attribute 'plot'

C TypeError: 'module' object is not callable

D No error, code runs and shows a plot

💡 Hint

matplotlib.pyplot is the submodule with plot and show functions.

The main matplotlib module does not have plot or show functions; they are in matplotlib.pyplot.

Practice

1. What is the main purpose of Matplotlib in data science?

easy

A. To perform complex mathematical calculations

B. To store large amounts of data efficiently

C. To create visual graphs and charts from data

D. To clean and prepare data for analysis

Solution

1. Step 1: Understand Matplotlib's role

   Matplotlib is a tool used to turn data into pictures like graphs and charts.

2. Step 2: Match purpose with options

   Only To create visual graphs and charts from data describes creating visual graphs and charts, which is Matplotlib's main use.

3. Final Answer:

   To create visual graphs and charts from data -> Option C

4. Quick Check:

   Matplotlib = Visual graphs [OK]

Hint: Matplotlib makes pictures from data [OK]

Common Mistakes:

• Confusing Matplotlib with data storage tools
• Thinking Matplotlib cleans data
• Assuming Matplotlib does math calculations

2. Which of the following is the correct way to import Matplotlib's plotting module?

easy

A. import matplotlib.pyplot as plt

B. import matplotlib.plot as plt

C. import matplotlib.graph as plt

D. import matplotlib.chart as plt

Solution

1. Step 1: Recall Matplotlib import syntax

   The standard way to import the plotting module is 'import matplotlib.pyplot as plt'.

2. Step 2: Compare options

   Only import matplotlib.pyplot as plt uses the correct module name 'pyplot' and alias 'plt'. Others use incorrect module names.

3. Final Answer:

   import matplotlib.pyplot as plt -> Option A

4. Quick Check:

   Correct import = import matplotlib.pyplot as plt [OK]

Hint: Remember 'pyplot' and alias 'plt' for plotting [OK]

Common Mistakes:

• Using wrong module names like 'plot' or 'graph'
• Forgetting the alias 'plt'
• Confusing import syntax with other libraries

3. What will the following code display?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.show()

medium

A. No graph will be shown due to error

B. A bar chart with bars at 1, 2, and 3

C. A scatter plot with points at (4,1), (5,2), and (6,3)

D. A line graph connecting points (1,4), (2,5), and (3,6)

Solution

1. Step 1: Understand plt.plot() usage

   The plt.plot() function draws a line graph connecting points from x and y lists.

2. Step 2: Analyze given points

   Points are (1,4), (2,5), and (3,6), so a line graph connects these points.

3. Final Answer:

   A line graph connecting points (1,4), (2,5), and (3,6) -> Option D

4. Quick Check:

   plt.plot() = line graph [OK]

Hint: plt.plot() draws lines between points [OK]

Common Mistakes:

• Confusing plt.plot() with bar or scatter plots
• Mixing up x and y coordinates
• Expecting no output due to misunderstanding plt.show()

4. Identify the error in this Matplotlib code:

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5])
plt.show()

medium

A. plt.show() is called before plt.plot()

B. The x and y lists have different lengths causing an error

C. Missing import statement for pyplot

D. No error, code runs fine

Solution

1. Step 1: Check lengths of x and y lists

   The x list has 3 elements, y list has 2 elements, which is invalid for plotting.

2. Step 2: Understand Matplotlib requirements

   Matplotlib requires x and y lists to be the same length to plot points correctly.

3. Final Answer:

   The x and y lists have different lengths causing an error -> Option B

4. Quick Check:

   Equal length lists needed [OK]

Hint: Check x and y list lengths match [OK]

Common Mistakes:

• Ignoring list length mismatch
• Thinking plt.show() order matters here
• Assuming import is missing when it is present

5. You want to create a bar chart showing sales for products A, B, and C with values 10, 15, and 7. Which code correctly does this using Matplotlib?

hard

A. import matplotlib.pyplot as plt
products = ['A', 'B', 'C']
sales = [10, 15, 7]
plt.bar(products, sales)
plt.show()

B. import matplotlib.pyplot as plt
plt.plot(['A', 'B', 'C'], [10, 15, 7])
plt.show()

C. import matplotlib.pyplot as plt
plt.scatter(['A', 'B', 'C'], [10, 15, 7])
plt.show()

D. import matplotlib.pyplot as plt
plt.hist([10, 15, 7])
plt.show()

Solution

1. Step 1: Identify bar chart function

   Matplotlib's plt.bar() creates bar charts using categories and values.

2. Step 2: Check code correctness

   import matplotlib.pyplot as plt products = ['A', 'B', 'C'] sales = [10, 15, 7] plt.bar(products, sales) plt.show() uses plt.bar() with product names and sales values, then shows the plot.

3. Final Answer:

   Code using plt.bar() with products and sales lists -> Option A

4. Quick Check:

   Bar chart needs plt.bar() [OK]

Hint: Use plt.bar() for bar charts with categories [OK]

Common Mistakes:

• Using plt.plot() for bar charts
• Using plt.scatter() which makes scatter plots
• Using plt.hist() which makes histograms