Samacheer Kalvi Class 12 Computer Science Solutions Chapter 16 Data Visualization Using Pyplot: Line Chart, Pie Chart and Bar Chart

I. Choose the Best Answer (1 Mark)

 

Question 1. Which is a python package used for 2D graphics?
(a) matplotlib.pyplot
(b) matplotlib.pip
(c) matplotlib.numpy
(d) matplotlib.plt
Answer: (a) matplotlib.pyplot
In simple words: Matplotlib is a very popular tool in Python that helps you draw different types of pictures, like graphs and charts, especially in two dimensions. Pyplot is a part of Matplotlib that makes it easy to create these plots.

🎯 Exam Tip: Remember that `matplotlib.pyplot` is the specific module within the Matplotlib library used for creating plots.

 

Question 2. Identify the package manager for Python packages, or modules.
(a) Matplotlib
(b) PIP
(c) plt.show()
(d) python package
Answer: (b) PIP
In simple words: PIP is like a special tool that helps you add new features and tools (called packages or modules) to your Python programs. It makes installing and managing them very easy.

🎯 Exam Tip: PIP stands for "Pip Installs Packages" and is the standard package installer for Python, essential for adding external libraries.

 

Question 3. Read the following code: Identify the purpose of this code and choose the right option from the following.
C:\Users\YourName\AppData\Local\Programs\Python\Python36-32\Scripts > pip - version
(a) Check if PIP is Installed
(b) Install PIP
(c) Download a Package
(d) Check PIP version
Answer: (d) Check PIP version
In simple words: When you type `pip --version` in the command line, it tells you which version of the PIP tool is currently installed on your computer. This helps you know if your PIP is up-to-date.

🎯 Exam Tip: The `--version` flag is a common command-line argument used to check the version of many software tools, not just PIP.

 

Question 4. Read the following code: Identify the purpose of this code and choose the right option from the following.
C:\Users\YourName\AppData\Local\Programs\Python\Python36-32\Scripts > pip list
(a) List installed packages
(b) list command
(c) Install PIP
(d) packages installed
Answer: (a) List installed packages
In simple words: The `pip list` command shows you all the Python tools and features that you have already installed on your computer. It's like checking a list of all your Python applications.

🎯 Exam Tip: `pip list` is useful for checking dependencies and ensuring all required packages are present in your Python environment.

 

Question 5. To install matplotlib, the following function will be typed in your command prompt. What does "-U"represents?
Python -m pip install -U pip
(a) downloading pip to the latest version
(b) upgrading pip to the latest version
(c) removing pip
(d) upgrading matplotlib to the latest version
Answer: (b) upgrading pip to the latest version
In simple words: The `-U` or `--upgrade` part in a command means you want to update the tool to its newest version. So, `-U pip` tells your computer to update the PIP tool itself.

🎯 Exam Tip: Always keep your package manager (like PIP) updated to avoid compatibility issues and access the latest features.

 

Question 6. Observe the output figure. Identify the coding for obtaining this output.
Question 2. Explain the various buttons in a matplotlib window.
Answer: The Matplotlib window has several useful buttons to help you interact with your charts.
* **Home Button:** This button takes you back to the very first view of your chart after you have navigated it. It's like a reset button for the view.
* **Forward/Back Buttons:** These buttons work similar to browser navigation. You can use them to move back to a previous view or forward to a later view you were just looking at.
* **Pan Axis Button:** This button lets you click and drag your chart around the screen. You can move the entire plot to see different areas.
* **Zoom Button:** With this button, you can click and drag a square area on your chart to zoom in very closely. A left-click and drag zooms in, while a right-click and drag zooms out.
* **Configure Subplots Button:** This button helps you change the spacing and layout of different plots within the same figure.
* **Save Figure Button:** This button allows you to save your chart in many different picture formats, like PNG or JPG.
In simple words: Matplotlib charts have buttons to help you move around, zoom in, change the layout, and save your graphs easily.

🎯 Exam Tip: Remember the function of each button, especially the difference between pan and zoom, as these are common operations when analyzing data visualizations.

 

Question 3. Explain the purpose of the following functions:
Answer: Here are the purposes of the Matplotlib functions:
a) **plt.xlabel():** This function is used to put a label on the X-axis of your graph. This label helps to explain what the data on the horizontal axis represents.
b) **plt.ylabel():** This function is used to put a label on the Y-axis of your graph. This label helps to explain what the data on the vertical axis represents.
c) **plt.title():** This function is used to set the main title for your entire graph or plot. It tells the viewer what the whole chart is about.
d) **plt.legend():** This function is used to show a legend on your plot. The legend helps identify different lines or bars on the graph, especially when you have multiple datasets.
e) **plt.show():** This function is used to display the plot window. Without it, the graph might be created in the background but won't pop up on your screen.
In simple words: These functions help you label your graph's sides (x and y axes), give it a main name (title), explain what different lines mean (legend), and finally, show the graph on your screen.

🎯 Exam Tip: Always include descriptive labels for axes and a clear title to make your visualizations understandable and professional.

 

I. Choose the best answer (1 Mark)

 

Question 1. .......... button is used to click and drag a graph around.
(a) pan axis
(b) home
(c) zoom
(d) drag
Answer: (a) pan axis
In simple words: The pan axis button lets you move the whole graph left, right, up, or down by clicking and dragging.

🎯 Exam Tip: Understand the unique action of each navigation button in Matplotlib to select the correct one for specific movements.

 

Question 2. .......... charts display information as series of data points.
(a) Bar
(b) Pie
(c) Line
(d) Histogram
Answer: (c) Line
In simple words: Line charts show information using a series of points connected by lines, which is good for showing changes over time.

🎯 Exam Tip: Line charts are ideal for showing trends over continuous intervals like time, while bar charts are better for comparing categories.

 

Question 3. The representation of information in a graphic format is called ..........
(a) chart
(b) graphics
Answer: (a) chart
In simple words: When information is shown as a picture, like a bar or line drawing, it is called a chart.

🎯 Exam Tip: Recognize that "chart" is a general term for many types of visual data representations.

 

Question 4. .......... refers to a graphical representation that displays data by way of bars to show the frequency of numerical data.
(a) Bar chart
(b) Line graph
(c) Pie chart
(d) Histogram
Answer: (d) Histogram
In simple words: A histogram uses bars to show how often different numbers or ranges of numbers appear in a dataset.

🎯 Exam Tip: Remember that histograms are specifically for displaying the frequency distribution of numerical data using contiguous bars.

 

Question 5. .......... represents the frequency distribution of continuous variables.
(a) Bar chart
(b) Line graph
(c) Pie chart
(d) Histogram
Answer: (d) Histogram
In simple words: Histograms are perfect for showing how continuous data, like heights or temperatures, are spread out.

🎯 Exam Tip: Distinguish between histograms (for continuous data distribution) and bar charts (for categorical data comparison).

 

Question 6. Find the Incorrect match from the following.
(a) Scatter plot – collection of points
(b) line charts – markers
(c) Box plot – Boxes
Answer: (c) Box plot – Boxes
In simple words: The question asks for the incorrect match. However, "Box plot – Boxes" is actually a correct statement because box plots use boxes to show data distribution. There might be an error in the question or options provided.

🎯 Exam Tip: Thoroughly understand the characteristics of each plot type to correctly identify their visual components.

 

Question 7. Which of the following plot we cannot rearrange the blocks from highest to lowest?
(a) Line
(b) Bar chart
(c) Pie chart
(d) Histogram
Answer: (d) Histogram
In simple words: In a histogram, the bars are usually shown in the order of the number ranges, so you cannot change their order from tallest to shortest like you can with a bar chart. Histograms show continuous data ranges in sequence.

🎯 Exam Tip: Remember that histograms show continuous data ranges sequentially, meaning the order of bars cannot be rearranged like categorical bar charts.

 

Question 8. In .......... graph, the width of the bars is always the same.
(a) Line
(b) Bar
(c) Pie chart
(d) Histogram
Answer: (b) Bar
In simple words: In a regular bar graph, all the bars that show different categories have the same width, only their height changes to show value.

🎯 Exam Tip: In a bar graph, consistent bar width makes comparisons between categories clear, as only the height represents the value.

 

Question 9. The .......... parameter allows us to display the percentage value using the Python string formatting in pie chart.
(a) percent
(b) autopct
(c) pet
(d) percentage
Answer: (b) autopct
In simple words: The 'autopct' setting in a pie chart lets you show the percentage of each slice right on the chart itself.

🎯 Exam Tip: The `autopct` parameter is crucial for making pie charts informative by displaying numerical percentages directly on the wedges.

 

Question 10. If a single list is given to the plot() command, matplotlib assumes
(a) it is as a sequence of x values
(b) the sequence of y values
Answer: (a) it is as a sequence of x values
In simple words: When you give only one list to `plot()`, Matplotlib automatically treats those numbers as the 'x' values, and then makes up the 'y' values itself.

🎯 Exam Tip: Remember that `plt.plot()` is flexible; if only one list is provided, it defaults to representing the Y-axis data, while the X-axis is automatically generated.

 

Question 11. .......... is the graphical representation of information and data.
(a) Data visualization
(b) Data Graphics
(c) Data Dimension
(d) Data Images
Answer: (a) Data visualization
In simple words: Data visualization is the process of showing information and data using pictures, like charts and graphs.

🎯 Exam Tip: Data visualization is the broad term for converting raw data into a visual format to make it easier to understand.

 

Question 12. .......... in data visualization helps to show the relationship in the data for more variables.
(a) Tables
(b) Graphics
(c) Charts
(d) Dashboards
Answer: (c) Charts
In simple words: Charts are visual tools used to display how different parts of your data relate to each other, especially when you have many types of information.

🎯 Exam Tip: Charts are versatile tools within data visualization for illustrating relationships and patterns among multiple variables.

 

Question 13. In a Scatter plot, the position of a point depends on its .......... value whether the horizontal or vertical dimension.
(a) 2-Dimensional
(b) 3-Dimensional
(c) Single Dimensional
(d) 4-Dimensional
Answer: (a) 2-Dimensional
In simple words: For a scatter plot, each point is placed using two values, one for how far across (horizontal) it is and one for how high up (vertical) it is.

🎯 Exam Tip: Scatter plots are inherently 2-dimensional, using an X and Y coordinate to define each point's position and show relationships between two variables.

 

Question 14. .......... plot shows the relationship between a numerical variable and a categorical variable.
(a) line
(b) Bar
(c) Scatter
(d) Box
Answer: (b) Bar
In simple words: A bar plot is used to compare a number value across different categories, like showing sales for different products.

🎯 Exam Tip: Bar charts excel at comparing numerical values across distinct categories, making them suitable for showing relationships between one numerical and one categorical variable.

 

Question 15. .......... is the representation of information in a graphic format.
(a) Infographics
(b) Graph
(c) Symbol
(d) Charts
Answer: (a) Infographics
In simple words: An infographic is a special kind of picture that uses visuals, charts, and minimal text to explain information quickly and clearly.

🎯 Exam Tip: Infographics are designed to present complex information visually and concisely, often combining text, images, and charts.

 

Question 16. .......... is a collection of resources assembled to create a single unified visual display.
(a) Infographics
(b) Dashboard
(c) Graph
(d) Charts
Answer: (b) Dashboard
In simple words: A dashboard is like a control panel that gathers different charts and information into one easy-to-see screen.

🎯 Exam Tip: Dashboards are used to provide a consolidated view of key data points, making it easy to monitor performance or track trends at a glance.

 

Question 17. Matplotlib is a data visualization .......... in Python.
(a) control structure
(b) dictionary
(c) library
(d) list
Answer: (c) library
In simple words: Matplotlib is like a collection of ready-made tools and functions in Python that programmers use to draw many different kinds of graphs.

🎯 Exam Tip: Remember that Matplotlib is a powerful and widely used library for creating static, animated, and interactive visualizations in Python.

 

Question 18. Matplotlib allows us to create different kinds of .......... ranging from histograms
(a) Table
(b) Charts
(c) Maps
(d) plots
Answer: (d) plots
In simple words: Matplotlib is a flexible tool that can make many kinds of plots, like bar graphs, line graphs, and histograms.

🎯 Exam Tip: Understand that "plots" is a general term encompassing various graphical representations of data, all creatable with Matplotlib.

 

Question 19. Which function shows the percentage value in the pie chart?
(c) slice
(d) autopct
Answer: (d) autopct
In simple words: The `autopct` setting is what makes the percentage numbers appear on each slice of a pie chart.

🎯 Exam Tip: Clearly differentiate `autopct` from other parameters when dealing with pie chart customization for percentage display.

 

Question 20. .......... command will take an arbitrary number of arguments.
(a) show ()
(b) plot ()
(c) legend ()
(d) title ()
Answer: (b) plot ()
In simple words: The `plot()` command is very flexible and can accept many different inputs to draw graphs, depending on how you want to show your data.

🎯 Exam Tip: Recognize `plt.plot()` as a highly versatile function that can interpret various input formats to create different types of line plots.

 

Question 21. The most popular data visualization library allows creating charts in few lines of code in python.
(a) Molplotlib
(b) Infographics
(c) Data visualization
(d) pip
Answer: (a) Molplotlib
In simple words: Matplotlib (often typed as Molplotlib due to OCR) is the most common Python library that makes it easy to draw different kinds of charts with just a few lines of code.

🎯 Exam Tip: Know that Matplotlib is the fundamental Python library for creating a wide range of plots and charts efficiently.

 

II. Answer the following questions (2 and 3 Marks)

 

Question 1. What is meant by Infographics?
Answer: An infographic, which is short for information graphic, is a way to show information in a visual and graphic format. It uses images, charts, and minimal text to explain complex data clearly and quickly. Infographics are very useful for presenting information in a way that is easy to understand and remember.
In simple words: Infographics are pictures that use visuals and charts to explain facts and data in a simple way.

🎯 Exam Tip: Highlight that infographics combine visual elements with text to communicate complex information effectively and engage the audience.

 

Question 2. Define Dashboard.
Answer: A dashboard is a special display that brings together many different resources, like charts, graphs, and other data visualizations, into one single screen. It helps to simplify complex ideas and concepts into a clear, visual format. By using a dashboard, people can easily see patterns and relationships in data that would be hard to spot in just text alone. They are great for quick monitoring and decision-making.
In simple words: A dashboard is a single screen that shows many charts and data pictures together, making it easy to understand lots of information at once.

🎯 Exam Tip: Emphasize that a dashboard provides a consolidated, unified view of key information, enabling quick analysis and pattern recognition.

 

Question 3. Write a note on matplotlib.
Answer: Matplotlib is a very popular data visualization library in Python. It is a powerful tool that helps users create many different kinds of charts and graphs with just a few lines of code. This library makes it easy to visualize data, whether you need a simple line plot or a complex scientific figure, by providing various plotting functions. Its flexibility and extensive features make it a go-to choice for data scientists and analysts.
In simple words: Matplotlib is a Python tool that helps you draw all sorts of graphs and charts easily.

🎯 Exam Tip: Remember Matplotlib as the foundational library in Python for creating static, interactive, and animated data visualizations.

 

Question 4. Write a note on the scatter plot.
Answer: A scatter plot is a type of graph that shows data points as a collection of individual dots. Each dot on the plot represents two pieces of information, with its position depending on two values: one for the horizontal (X) dimension and another for the vertical (Y) dimension. These plots are excellent for finding relationships or patterns between two different variables. For example, you can see if two things tend to increase together or if there is no clear connection.
In simple words: A scatter plot uses dots to show how two different sets of numbers are related. Each dot is placed based on an X and a Y value.

🎯 Exam Tip: Understand that scatter plots are primarily used to observe relationships, correlations, or clusters between two numerical variables.

 

Question 5. Define Box plot.
Answer: A box plot, also known as a box-and-whisker plot, is a standard way to show how data is spread out. It is based on a "five-number summary," which includes the smallest number (minimum), the first quarter value (first quartile), the middle number (median), the third quarter value (third quartile), and the largest number (maximum). This plot helps visualize the distribution, skewness, and potential outliers of numerical data in a simple, compact way.
In simple words: A box plot is a graph that shows how a set of numbers is spread out, using five key values like the smallest, largest, and middle numbers.

🎯 Exam Tip: Focus on the five-number summary (minimum, Q1, median, Q3, maximum) as the core components represented in a box plot.

 

III. Answer the following questions (5 Marks)

 

Question 1. Write the key differences between Histogram and bar graph.
Answer:

In simple words: Histograms show how often numbers appear in ranges, with no gaps between bars, and the order cannot change. Bar graphs compare categories, have gaps between bars, and can be reordered.

🎯 Exam Tip: Clearly state that histograms are for continuous numerical data with no gaps between bars, while bar graphs are for discrete categorical data with gaps.

 

Question 2. Explain the purpose of
(i) plt.plot()
(ii) plt.bar()
(iii) plt.xticks()
(iv) plt.pie()
Answer:
(i) **plt.plot():** This function is used to create a line chart or a general graph with Matplotlib. It connects data points with lines, showing trends over continuous data.
(ii) **plt.bar():** This function is used to create a bar chart with Matplotlib. It displays rectangular bars to compare numerical values across different categories.
(iii) **plt.xticks():** This function is used to display and customize the tick marks and labels along the X-axis. You can use it to set specific values or text labels at certain points on the X-axis.
(iv) **plt.pie():** This function is used to create a pie chart with Matplotlib. It shows data as slices of a circle, where each slice represents a proportion of the whole.
In simple words: `plt.plot()` draws line graphs, `plt.bar()` draws bar graphs, `plt.xticks()` changes labels on the X-axis, and `plt.pie()` makes pie charts.

🎯 Exam Tip: For each function, clearly describe what type of plot it creates or what specific part of a plot it controls, as these are fundamental to Matplotlib.

 

Question 3. Draw the output for the following python code:
`import matplotlib.pyplot as plt`
`a = [1,2,3]`
`b = [5,7,4]`
`x = [1,2,3]`
`y = [10,14,12]`
`plt.plot(a,b, label='Label 1')`
`plt.plot(x,y, label='Label 2')`
`plt.xlabel('X-Axis')`
`plt.ylabel('Y-Axis')`
`plt.legend()`
`plt.show()`
Answer: The code will produce a line graph with two distinct lines plotted on it.
* **Line 1 ('Label 1'):** Will connect points (1,5), (2,7), and (3,4).
* **Line 2 ('Label 2'):** Will connect points (1,10), (2,14), and (3,12).
The X-axis will be labeled "X-Axis" and the Y-axis will be labeled "Y-Axis". A legend will appear, clearly distinguishing "Label 1" and "Label 2" lines, typically by color or line style. The plot will show a range from about 1 to 3 on the X-axis and about 4 to 14 on the Y-axis, displaying how both sets of Y values change with increasing X values.
In simple words: This code will draw a graph with two separate lines. One line connects points like (1,5), and the other connects points like (1,10). The graph will have labels for X and Y axes and a small box explaining which line is which.

🎯 Exam Tip: When describing graph outputs from code, mention the number of lines, their data points, axis labels, and the presence of a legend.

 

Question 4. Draw the chart for the given Python snippet.
`import matplotlib.pyplot as plt`
`plt.plot([1,2,3,4], [1,4,9,16])`
`plt.show()`
Answer: This Python code will generate a simple line graph.
The graph will plot four points: (1,1), (2,4), (3,9), and (4,16). These points will be connected by straight line segments, creating a curve that rises sharply. The X-axis values will range from 1 to 4, and the Y-axis values will range from 1 to 16. This particular curve shows a quadratic relationship, where Y is the square of X, making the line increasingly steep as X increases.
In simple words: The code will draw a line graph connecting four points: (1,1), (2,4), (3,9), and (4,16). This line will curve upwards sharply.

🎯 Exam Tip: Pay attention to the coordinates for each point to accurately visualize the shape and trend of the plotted line.

 

Hands-on Practice

 

Question 1. Create a plot. Set the title, the x and y labels for both axes,
`import matplotlib.pyplot as plt`
`x=[1,2,3]`
`Y=[5,7,4]`
`plt.plot(x,Y)`
`plt.xlabel('X-AXIS')`
`plt.ylabel('Y-AXIS')`
`plt.title('LINE GRAPH')`
`plt.show()`
Answer: This code will create and display a line graph.
The graph will plot three points: (1,5), (2,7), and (3,4). These points will be connected by line segments. The X-axis will be clearly labeled "X-AXIS", and the Y-axis will be labeled "Y-AXIS". The entire graph will have a main title "LINE GRAPH". The plot will visually show how the Y values change as the X values increase, first rising and then falling. This setup ensures that the graph is well-defined and easy for anyone to understand at a glance.
In simple words: This Python code will show a line graph. It connects points (1,5), (2,7), and (3,4). The graph will have "X-AXIS" and "Y-AXIS" written on its sides, and "LINE GRAPH" as its main title.

🎯 Exam Tip: Always include `plt.xlabel()`, `plt.ylabel()`, and `plt.title()` in your plotting code for clarity and completeness.

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