Data Visualization

1. DATA
VISUALIZATION
(matplotlib.pyplot)

2. Data Visualization
 Purpose of plotting;
 drawing and saving following types of plots using
matplotlib – line plot, bar graph, histogram, pie
chart, frequency polygon, box plot and scatter
plot.
 Customizing plots: color, style (dashed, dotted),
width; adding label, title, and legend in plots.
1
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3. Purpose of Plotting 2
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 One of the most popular uses for Python is data analysis.
Data scientists want a way to visualize their data to get a
better grasp of the data, and to convey their results to
someone.
 Matplotlib is a Python library used for plotting. It is used to
create 2d Plots and graphs easily and control font properties,
line controls, formatting axes, etc. through Python script.

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

5. Line Chart 3
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import matplotlib.pyplot as plt
plt.plot([‘A’,’B’,’C’],[4,5,1])
plt.show()
import matplotlib.pyplot as plt
plt.plot([1,5],[2,6])
plt.show()

6. Line Chart
Try all the commands
4
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import matplotlib.pyplot as plt
x = ['A1','B1','C1']
y = [31,27,40]
x1 = ['A1','B1','C1','D1']
y1 = [12,20,19,17]
plt.plot(x,y,label = "Sr. School")
plt.plot(x1,y1,label = "Jr.School")
plt.title("Bus Info")
plt.ylabel("No. of Students")
plt.xlabel("Bus No.")
plt.legend()
plt.savefig("businfo")
plt.show()
Title
xlabel
ylabel Legend

7. Line Chart 5
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Save the figure
plt.savefig(“linechart.pdf”)
# saves in the current directory
plt.savefig(“c:datamultibar.pdf”)
# saves in the given path
plt.savefig(“c:datamultibar.png”)
# saves in the given path in .png format

8. Bar Chart 9
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import matplotlib.pyplot as plt
# Students in each section
x = ['A','B','C','D','E']
y = [31,27,40,43,45]
plt.bar(x,y,label = "No.of students")
plt.title("Section wise number of students")
plt.ylabel("No. of Students")
plt.xlabel("Section")
plt.legend()
plt.show()

9. Bar Chart Horizontal 10
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import matplotlib.pyplot as plt
# Students in each section
x = ['A','B','C','D','E']
y = [31,27,40,43,45]
plt.barh(x,y,label = "No.of students")
plt.title("Section wise number of students")
plt.ylabel("No. of Students")
plt.xlabel("Section")
plt.legend()
plt.show()

10. Bar Chart Stacked 11
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import matplotlib.pyplot as plt
# Number of students in each bus
x = [‘A’, ‘B’, ‘C’, ‘D’]
y = [31,27,40,32]
y1 = [12,20,19,17]
plt.bar(x,y,label = "Sr. School")
plt.bar(x,y1,label = "Jr.School")
plt.title("Bus Info")
plt.ylabel("No. of Students")
plt.xlabel("Bus No.")
plt.legend()
plt.show()

11. Bar Chart – Multiple 12
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import matplotlib.pyplot as plt
import numpy as np
# Number of students in each bus
x = np.arange(1,5)
y = [31,27,40,32]
y1 = [12,20,19,17]
plt.bar(x+0,y,label = "Sr. School",width = 0.4)
plt.bar(x+0.4,y1,label = "Jr.School",width = 0.4)
plt.title("Bus Info")
plt.ylabel("No. of Students")
plt.xlabel("Bus No.")
plt.legend()
plt.show()

12. Histogram 13
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import matplotlib.pyplot as plt
import numpy as np
# Marks obtained by 50 students
x = [5,15,20,25,35,45,55]
y = np.arange(0,61,10)
w = [2,3,8,9,12,6,10]
plt.hist(x,bins = y, weights = w,
label = "Marks Obtained")
plt.title("Histogram")
plt.ylabel("Marks Range")
plt.xlabel("No. of Students")
plt.legend()
plt.show()

13. Histogram 13
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import matplotlib.pyplot as plt
import numpy as np
# Marks obtained by 50 students
x = [5,15,20,25,35,45,55,70,84,90,93]
y = [0,33,45,60,75,90,100]
w = [2,3,8,9,12,6,10,5,8,12,7]
plt.hist(x,bins = y, weights = w,
label = "Marks Obtained",
edgecolor = "yellow")
plt.title("Histogram")
plt.ylabel("Marks Range")
plt.xlabel("No. of Students")
plt.legend()
plt.show()

14. Difference between Bar graph and Histogram 13
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15. Difference between Bar graph and Histogram 14
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Histogram Bar
Histogram is defined as a type of bar chart that to
show the frequency distribution of continuous data.
It indicates the number of observations which lie in-
between the range of values, known as class or bin.
Take the observations and split them into logical
series of intervals called bins.
X-axis indicates, independent variables i.e. bins
Y-axis represents dependent variables i.e.
occurrences.
Rectangle blocks i.e. bars are shown on the x-axis,
whose area depends on the bins.
A bar graph is a chart that represents the comparison
between categories of data.
It displays grouped data by way of parallel rectangular
bars of equal width but varying the length.
Each rectangular block indicates specific category and
the length of the bars depends on the values they
hold. The bars do not touch each other.
Bar diagram can be horizontal or vertical, where a
horizontal bar graph is used to display data varying
over space whereas the vertical bar graph represents
time series data. It contains two axis, where one axis
represents the categories and the other axis shows
the discrete values of the data.

16. Difference between Bar graph and Histogram 15
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Histogram Bar
A graphical representation to
show the frequency of numerical
data.
A pictorial representation of data
to compare different category of
data.
Bars touch each other, hence
there are no spaces between
bars.
Bars do not touch each other,
hence there are spaces between
bars.
The width of bar may or may not
same (depends on bins)
The width of bar remain same.

17. CBSE Questions 16
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Fill in the blanks :
1. The command used to give a heading to a graph is _________
a. plt.show()
b. plt.plot()
c. plt.xlabel()
d. plt.title()
2. Using Python Matplotlib _________ can be used to count how
many values fall into each interval
a. line plot
b. bar graph
c. histogram

18. CBSE Questions 17
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Fill in the blanks :
1. The command used to give a heading to a graph is _________
a. plt.show()
b. plt.plot()
c. plt.xlabel()
d. plt.title()
2. Using Python Matplotlib _________ can be used to count how
many values fall into each interval
a. line plot
b. bar graph
c. histogram
plt.title()
histogram

19. CBSE Questions 18
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Rashmi wants to plot a bar graph for the department name on x
– axis and number of employees in each department on y-axis.
Complete the code to perform the following:
(i) To plot the bar graph in statement 1
(ii) To display the graph on screen in statement 2
import matplotlib as plt
x = [‘Marketing’, ‘Office’, ‘Manager’, ‘Development’]
y = [ 35, 29, 30, 25]
_______________________________ Statement 1
_______________________________ Statement 2

20. CBSE Questions 19
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Rashmi wants to plot a bar graph for the department name on x
– axis and number of employees in each department on y-axis.
Complete the code to perform the following:
(i) To plot the bar graph in statement 1
(ii) To display the graph on screen in statement 2
import matplotlib as plt
x = [‘Marketing’, ‘Office’, ‘Manager’, ‘Development’]
y = [ 35, 29, 30, 25]
_______________________________ Statement 1
_______________________________ Statement 2
plt.bar(x,y)
plt.show()

21. CBSE Questions 20
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Anamica wants to draw a line chart using a list of elements
named L. Complete the code to perform the following
operations:
(i) To plot a line chart using the list L
(ii) To give a y-axis label to the line chart as “List of Numbers”
import matplotlib.pyplot as plt
L = [10, 12, 15, 18, 25, 35, 50, 76, 89]
_______________________________ Statement 1
________________________________ Statement 2
plt.show()

22. CBSE Questions 21
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Anamica wants to draw a line chart using a list of elements
named L. Complete the code to perform the following
operations:
(i) To plot a line chart using the list L
(ii) To give a y-axis label to the line chart as “List of Numbers”
import matplotlib.pyplot as plt
L = [10, 12, 15, 18, 25, 35, 50, 76, 89]
_______________________________ Statement 1
________________________________ Statement 2
plt.show()
plt.plot(L)
plt.ylabel(“List of Numbers”)

23. CBSE Questions 22
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Write a code to plot the speed of a passenger train as shown in
the figure given below.

24. CBSE Questions 23
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Write a code to plot the speed of a passenger train as shown in
the figure given below.
import matplotlib.pyplot as plt
import numpy as np
x = np.arange(1, 5)
plt.plot(x, x*2.0, label='Normal')
plt.plot(x, x*3.0, label='Fast')
plt.plot(x, x/2.0, label='Slow')
plt.legend()
plt.show()

25. CBSE Questions 24
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Consider the following graph . Write the code to plot it.

26. CBSE Questions 25
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Consider the following graph . Write the code to plot it.
SOLUTION 1
import matplotlib.pyplot as plt
plt.plot([2,7],[1,6])
plt.show()
SOLUTION 2
import matplotlib.pyplot as plt
Y = [1,2,3,4,5,6]
X = [2,3,4,5,6,7]
plt.plot (X, Y)

27. CBSE Questions 26
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Draw the following bar graph representing the number of
students in each class.

28. CBSE Questions 27
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Draw the following bar graph representing the number of students in
each class.
import matplotlib.pyplot as plt
Classes = ['VII','VIII','IX','X']
Students = [40,45,35,44]
plt.bar(classes, students)
plt.show()

29. CBSE Questions 28
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Write a code to plot a bar chart to depict the pass
percentage of students in CBSE exams for the last four years
as shown below:

30. CBSE Questions 29
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Write a code to plot a bar chart to depict the pass
percentage of students in CBSE exams for the last four years
as shown below:
import matplotlib.pyplot as plt
objects= ["Year1","Year2","Year3","Year4"]
percentage=[82,83,85,90]
plt.bar(objects, percentage)
plt.ylabel("Pass Percentage")
plt.xlabel("Years")
plt.show()

31. CBSE Questions 30
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Mr. Vinay wants to plot line charts to compare the trend in the price of diesel and
petrol over the last few weeks from the following data in Python Lists. Help him
write the complete code by filling in the blanks :
(i) To plot the price of diesel in statement 1
(ii) To plot the price of petrol in statement 2
(iii) To give a suitable heading to the graph in statement 3
(iv) To display the legends in statement 4
(v) To display the graph in statement 5
import matplotlib.pyplot as plt
petrol = [ 80 , 82 , 82.50 , 81, 81.50 ]
diesel = [ 73 , 77 , 74 , 74.5 , 75.4 ]
_____________________ Statement 1
_____________________ Statement 2
_____________________ Statement 3
_____________________ Statement 4
_____________________ Statement 5

32. CBSE Questions 31
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Mr. Vinay wants to plot line charts to compare the trend in the price of diesel and
petrol over the last few weeks from the following data in Python Lists. Help him
write the complete code by filling in the blanks :
(i) To plot the price of diesel in statement 1
(ii) To plot the price of petrol in statement 2
(iii) To give a suitable heading to the graph in statement 3
(iv) To display the legends in statement 4
(v) To display the graph in statement 5
import matplotlib.pyplot as plt
petrol = [ 80 , 82 , 82.50 , 81, 81.50 ]
diesel = [ 73 , 77 , 74 , 74.5 , 75.4 ]
_____________________ Statement 1
_____________________ Statement 2
_____________________ Statement 3
_____________________ Statement 4
_____________________ Statement 5
plt.plot(diesel)
plt.plot(petrol)
plt.title(‘Price of Diesel vs petrol’)
plt.legend(‘Diesel’,’Petrol’)
plt.show()

33. CBSE Questions 32
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Mr. Vinay wants to plot line charts to compare the trend in the price of diesel and petrol over
the last few weeks from the following data in Python Lists. Help him write the complete code
by filling in the blanks :
Following is the data ( in hours ) of screen time spent on a device by sample students:
6,6,5,7,9,7,4,5,4,5,7,8,4,5,7,6,5,7,8,4,3,3,6,5.
The data is plotted to generate a histogram as follows:
Fill in the blanks to complete the code:
(i) To plot the histogram from the given data in Statement1
(ii) To save the figure as “Plot3.png” in Statement2
import matplotlib.pyplot as plt
hours =[6,6,5,7,9,7,4,5,4,5,7,8,4,5,7,6,5,7,8,4,3,3,6,5]
______________________ # Statement1
______________________ # Statement2

34. CBSE Questions 33
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Mr. Vinay wants to plot line charts to compare the trend in the price of diesel and petrol over
the last few weeks from the following data in Python Lists. Help him write the complete code
by filling in the blanks :
Following is the data ( in hours ) of screen time spent on a device by sample students:
6,6,5,7,9,7,4,5,4,5,7,8,4,5,7,6,5,7,8,4,3,3,6,5.
The data is plotted to generate a histogram as follows:
Fill in the blanks to complete the code:
(i) To plot the histogram from the given data in Statement1
(ii) To save the figure as “Plot3.png” in Statement2
import matplotlib.pyplot as plt
hours =[6,6,5,7,9,7,4,5,4,5,7,8,4,5,7,6,5,7,8,4,3,3,6,5]
______________________ # Statement1
______________________ # Statement2
plt.hist(hours)
plt.savefig(‘plot3.png’)

35. Subplots 34
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import matplotlib.pyplot as plt
fig,a = plt.subplots(2,2)
import numpy as np
x = np.arange(1,5)
y = [25,23,19,16]
y1 = [15,20,25,35]
fig.suptitle("Four Graphs")
a[0][0].plot(x,y,color = "g")
a[0][0].set_title('Line chart')
a[0][1].bar(x,y,color = "r")
a[0][1].set_title('Bar chart')
a[1][0].hist(y1,weights = [9,12,15,25],bins
=[10,20,30,40],color = "y",edgecolor = "b")
a[1][0].set_title('Histogram chart')
a[1][1].barh(x,y)
a[1][1].set_title('Horizontal Bar chart')
plt.show()