Horizontal bar chart with plt.barh in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of plt.barh with given data

What will be the output of this code snippet that creates a horizontal bar chart?

Matplotlib

import matplotlib.pyplot as plt

categories = ['A', 'B', 'C']
values = [3, 7, 5]
plt.barh(categories, values)
plt.show()

A A vertical bar chart with bars for A=3, B=7, C=5

B SyntaxError due to wrong function usage

C A horizontal bar chart with bars for A=7, B=3, C=5

D A horizontal bar chart with bars for A=3, B=7, C=5

💡 Hint

plt.barh creates horizontal bars where the first argument is the y-axis labels and the second is the bar lengths.

plt.barh(categories, values) draws horizontal bars with categories on the y-axis and values as bar lengths. The order matches the lists.

❓ data_output

intermediate

Number of bars in plt.barh chart

How many bars will be displayed by this code?

Matplotlib

import matplotlib.pyplot as plt

labels = ['X', 'Y', 'Z', 'W']
values = [10, 20, 15, 5]
plt.barh(labels, values)
plt.show()

A 3

B 4

C 5

D 0

💡 Hint

Count the number of labels given to plt.barh.

There are 4 labels and 4 values, so 4 horizontal bars will be drawn.

🔧 Debug

advanced

Identify the error in horizontal bar chart code

What error will this code produce?

Matplotlib

import matplotlib.pyplot as plt

labels = ['Jan', 'Feb', 'Mar']
values = [5, 8]
plt.barh(labels, values)
plt.show()

A ValueError: y and width must be the same size

B TypeError: unsupported operand type(s)

C No error, chart displays correctly

D SyntaxError due to missing colon

💡 Hint

Check if the lengths of labels and values match.

plt.barh requires the labels and values lists to be the same length. Here, labels has 3 items but values has 2, causing a ValueError.

❓ visualization

advanced

Effect of changing bar height in plt.barh

What visual effect does changing the 'height' parameter in plt.barh have?

Matplotlib

import matplotlib.pyplot as plt

labels = ['P', 'Q', 'R']
values = [4, 6, 8]
plt.barh(labels, values, height=0.1)
plt.show()

A Bars change color

B Bars become wider horizontally

C Bars become thinner vertically

D Bars disappear

💡 Hint

Height controls the thickness of horizontal bars.

In plt.barh, the height parameter controls the thickness of each horizontal bar vertically. Smaller height means thinner bars.

🚀 Application

expert

Create a horizontal bar chart with sorted values

Which code snippet correctly creates a horizontal bar chart with categories sorted by their values in ascending order?

A

import matplotlib.pyplot as plt
categories = ['A', 'B', 'C']
values = [5, 2, 7]
sorted_pairs = sorted(zip(values, categories))
sorted_values, sorted_categories = zip(*sorted_pairs)
plt.barh(sorted_categories, sorted_values)
plt.show()

B

import matplotlib.pyplot as plt
categories = ['A', 'B', 'C']
values = [5, 2, 7]
plt.barh(categories.sort(), values.sort())
plt.show()

C

import matplotlib.pyplot as plt
categories = ['A', 'B', 'C']
values = [5, 2, 7]
plt.barh(sorted(categories), sorted(values))
plt.show()

D

import matplotlib.pyplot as plt
categories = ['A', 'B', 'C']
values = [5, 2, 7]
plt.barh(categories, values)
plt.show()

💡 Hint

You need to sort values and categories together to keep their pairs aligned.

Option A sorts the pairs of (value, category) so the bars appear in ascending order by value. Other options either misuse sort or break the pairing.