Grouped bar charts in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of grouped bar chart code

What will be the height of the first bar in the first group when this code runs?

Matplotlib

import matplotlib.pyplot as plt

labels = ['A', 'B', 'C']
values1 = [5, 7, 3]
values2 = [6, 2, 4]

x = range(len(labels))
width = 0.35

fig, ax = plt.subplots()
ax.bar(x, values1, width, label='Group 1')
ax.bar([p + width for p in x], values2, width, label='Group 2')
plt.show()

A 3

B 6

C 5

D 7

💡 Hint

Look at the values1 list and the first bar plotted.

The first bar in the first group corresponds to the first value in values1, which is 5.

❓ data_output

intermediate

Number of bars in grouped bar chart

How many bars will be displayed in total when this grouped bar chart code runs?

Matplotlib

import matplotlib.pyplot as plt

labels = ['X', 'Y', 'Z', 'W']
values1 = [1, 2, 3, 4]
values2 = [4, 3, 2, 1]
values3 = [2, 3, 4, 5]

x = range(len(labels))
width = 0.2

fig, ax = plt.subplots()
ax.bar(x, values1, width, label='Set 1')
ax.bar([p + width for p in x], values2, width, label='Set 2')
ax.bar([p + 2*width for p in x], values3, width, label='Set 3')
plt.show()

A 16

B 12

C 8

D 4

💡 Hint

Count bars per group and multiply by number of groups.

There are 4 labels and 3 sets, so total bars = 4 * 3 = 12.

❓ visualization

advanced

Identify the correct grouped bar chart

Which option shows the correct grouped bar chart for these data sets?

Matplotlib

import matplotlib.pyplot as plt

labels = ['Jan', 'Feb', 'Mar']
sales_A = [10, 15, 7]
sales_B = [12, 9, 14]

x = range(len(labels))
width = 0.4

fig, ax = plt.subplots()
ax.bar(x, sales_A, width, label='Product A')
ax.bar([p + width for p in x], sales_B, width, label='Product B')
plt.xticks([p + width/2 for p in x], labels)
plt.legend()
plt.show()

A Bars for Product A and Product B are plotted with large gaps between each bar.

B Bars for Product A and Product B overlap exactly at each label position.

C Bars for Product A and Product B are stacked on top of each other.

D Bars for Product A and Product B are side by side with a small gap between groups.

💡 Hint

Grouped bars are side by side, not stacked or overlapping.

The code shifts the second set of bars by width, so bars appear side by side with small gaps.

🔧 Debug

advanced

Error in grouped bar chart code

What error will this code produce when run?

Matplotlib

import matplotlib.pyplot as plt

labels = ['A', 'B']
values1 = [3, 5, 7]
values2 = [2, 4]

x = range(len(labels))
width = 0.3

fig, ax = plt.subplots()
ax.bar(x, values1, width, label='Set 1')
ax.bar([p + width for p in x], values2, width, label='Set 2')
plt.show()

A ValueError: x and height must have same first dimension

B TypeError: unsupported operand type(s) for +: 'range' and 'float'

C IndexError: list index out of range

D No error, chart displays correctly

💡 Hint

Check if the lengths of x and values1 match.

values1 has 3 items but x has length 2, causing a ValueError about dimension mismatch.

🚀 Application

expert

Calculate total height per group from grouped bar chart data

Given these grouped bar chart data, what is the total height of bars for label 'C'?

Matplotlib

labels = ['A', 'B', 'C', 'D']
values1 = [4, 5, 6, 7]
values2 = [1, 2, 3, 4]
values3 = [7, 8, 9, 10]

A 18

B 22

C 9

D 15

💡 Hint

Add the values for label 'C' from all three lists.

For label 'C' (index 2), sum is 6 + 3 + 9 = 18.