Check your understanding of the previous reading: the kinds of plots and what they show, making a plot appear with show, combining plots, importing MatPlotLib, and reading a histogram.

Question 1

Match the type of graph with the kind of information that that type of graph conveys.

#	Information	Type of graph
1	The relationship between two lists of numbers
2	The distribution of a list of numbers
3	The trend in a list of numbers

Question 2

Write the final function call that should be used after the following code, in order to actually make the plot appear:

import matplotlib.pyplot as plt

plt.hist([1, 7, 5, 4, 3, 5, 6, 7])

Show worked solution

plt.show(). If you do not call the show function, no graph appears. It takes no arguments, but it still needs the parentheses: without them you are not actually calling the function.

Question 3

How many graphs will the following code create?

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

Select one answer, then check.

0
Not quite. The code calls show, so a graph does appear.
1
Correct. Both line plots are made before show is called, so they are combined on the same canvas: one graph, with the two identical lines on top of each other.
2
Not quite. Plots made before calling show are combined on the same canvas. You would need a show call after each plot to get two graphs.
3
Not quite. The code makes two line plots, and both come before the single call to show, so they end up on one graph.

Question 4

How many times do you need to import MatPlotLib?

Select one answer, then check.

None, because it is built-in to Python.
Not quite. MatPlotLib is an external library: a program that makes plots starts with import matplotlib.pyplot as plt.
Once, at the start of the program.
Correct. The import goes at the start of the program; after that, plt is available for every plot the program makes.
Once, at the end of the program.
Not quite. Python runs the program from top to bottom, so plt only exists after the import has run. At the end of the program it comes too late.
Once for each time that you are plotting, before you plot.
Not quite. One import is enough: after it, plt stays available for every plot in the program.

Question 5

Bar graphs and Histograms are basically the same thing.

Select one answer, then check.

True
Not quite. The reading warns not to confuse them: bar charts tell you the frequency of categories of data, while histograms group a list of numbers into bins, or ranges of numbers.
False
Correct. Bar charts are a more generalized kind of graph that tell you the frequency of categories of data; histograms take a list of numbers and group them into bins, or ranges of numbers, to show their distribution.

Question 6

Assume that a library exists that can get lists of integers representing students' grades.

from bakery_grades import get_grades
import matplotlib.pyplot as plt

grades = get_grades()

plt.hist(grades)
plt.show()

Executing the code above generates this image:

Which of the following statements is the best interpretation of the graph?

Select one answer, then check.

Many students got a 100.
Not quite. The bar at 100 is one of the shortest: only a handful of students.
Many students got a 0.
Not quite. The bar at 0 is the shortest of all: only a couple of students.
Many students got between 50 and 60.
Correct. The bin from 50 to 60 has the tallest bar, about 100 students.
Grades were very evenly distributed.
Not quite. Evenly distributed grades would give bars of about the same height. Here the bars rise to a peak in the middle and fall off towards both ends.