🔵 Data Science · Lesson 40

Data Visualization with Matplotlib

What is Data Visualization with Matplotlib?

Data Visualization with Matplotlib means data visualization presents data using charts so patterns, trends and comparisons become easier to understand.

In real programs, this topic helps in showing marks trends. Learn the idea first, then type the program yourself and compare the output.

💡 At a Glance

Point	Details
Course Area	Data Science Tools and concepts used to analyse, clean and present data.
Main Use	showing marks trends
Example File	`data-visualization-matplotlib.py`
Practice Focus	Run, change values, and explain the output line by line.

Why should you learn this?

It is useful for showing marks trends.
It connects with comparing categories.
It improves your ability to read, write and debug Python programs.

Important Terms

These terms are used directly in this lesson. Understand them before memorising the code.

Term	Meaning
plot	Graphical representation of data.
bar chart	Chart used to compare categories.
line chart	Chart used to show trends over time.
xlabel	xlabel is an important term in this topic.
ylabel	ylabel is an important term in this topic.

Syntax / Basic Pattern

The simple pattern is: prepare data, apply the concept, then show the result.

Basic Pattern

import matplotlib.pyplot as plt
subjects = ["Maths", "Science", "English"]
marks = [88, 92, 84]
plt.bar(subjects, marks)
plt.title("Subject-wise Marks")
plt.xlabel("Subjects")
plt.ylabel("Marks")
plt.show()

Complete Example Program

Python – data-visualization-matplotlib.py

import matplotlib.pyplot as plt

subjects = ["Maths", "Science", "English"]
marks = [88, 92, 84]

plt.bar(subjects, marks)
plt.title("Subject-wise Marks")
plt.xlabel("Subjects")
plt.ylabel("Marks")
plt.show()

Expected Output

A bar chart will be displayed.

Program Explanation

import matplotlib.pyplot as plt imports ready-made features from a module/library.
subjects = ["Maths", "Science", "English"] stores a value in subjects.
marks = [88, 92, 84] stores a value in marks.
plt.bar(subjects, marks) performs the next step of the program logic.
plt.title("Subject-wise Marks") performs the next step of the program logic.
plt.xlabel("Subjects") performs the next step of the program logic.
plt.ylabel("Marks") performs the next step of the program logic.

Where will you use it?

Showing marks trends.
Comparing categories.
Making dashboard charts.

Common Mistakes

Analysing data before checking missing values, duplicates and data types.
Changing original data without keeping a clean copy.
Creating charts without title, labels or explanation.

Practice Tasks

Type the program in data-visualization-matplotlib.py and run it.
Change input values or sample data and observe the new output.
Create one example related to showing marks trends.
Write 5 lines explaining the logic in your own words.

Summary

Data Visualization with Matplotlib is not a theory-only topic. You should be able to explain the meaning, write the example, run it successfully, and use it in a small practical program.

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