Bubble charts concept in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Bubble Chart Size Scaling

What will be the size of the bubbles in the plot generated by the following code snippet?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5, 6]
sizes = [10, 20, 30]
plt.scatter(x, y, s=sizes)
plt.show()
print(sizes)

A [100, 400, 900]

B [10, 20, 30]

C [1, 2, 3]

D [10, 20, 30, 40]

💡 Hint

The 's' parameter in plt.scatter controls the area of each bubble, not the radius.

The sizes list is passed directly to the 's' parameter, which sets the area of each bubble in points squared. The printed sizes list remains unchanged.

❓ data_output

intermediate

Number of Bubbles Displayed

Given the following data and code, how many bubbles will appear in the bubble chart?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 30, 40]
sizes = [15, 25, 35]
plt.scatter(x, y, s=sizes)
plt.show()

A Raises ValueError

B 4

C 3

D 0

💡 Hint

The lengths of x, y, and sizes must match for plt.scatter.

The sizes list has fewer elements than x and y, causing a ValueError due to mismatched array lengths.

❓ visualization

advanced

Interpreting Bubble Chart Colors and Sizes

Consider this code that creates a bubble chart with color and size representing different data aspects. What does the color represent in the resulting plot?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np
x = np.array([5, 15, 25, 35, 45])
y = np.array([10, 20, 30, 40, 50])
sizes = np.array([100, 200, 300, 400, 500])
colors = np.array([1, 2, 3, 4, 5])
plt.scatter(x, y, s=sizes, c=colors, cmap='viridis')
plt.colorbar()
plt.show()

A The colors represent the sizes of the bubbles.

B The colors represent the x-axis values.

C The colors are randomly assigned and do not represent any data.

D The colors represent the values in the 'colors' array, mapped to the 'viridis' color scale.

💡 Hint

The 'c' parameter controls color mapping in plt.scatter.

The 'c' parameter is set to the 'colors' array, so bubble colors correspond to these values mapped through the 'viridis' colormap.

🔧 Debug

advanced

Identify the Error in Bubble Chart Code

What error will this code produce when run?

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [4, 5]
sizes = [10, 20, 30]
plt.scatter(x, y, s=sizes)
plt.show()

A ValueError: x and y must be the same size

B TypeError: sizes must be a scalar or array-like

C IndexError: list index out of range

D No error, plot displays correctly

💡 Hint

Check if x and y have the same number of elements.

x has 3 elements but y has 2, causing ValueError due to mismatched input sizes for scatter plot.

🚀 Application

expert

Choosing Bubble Sizes for Visual Clarity

You have data points with values ranging from 1 to 1000. You want to create a bubble chart where bubble sizes reflect these values but remain visually clear and not too large. Which approach is best to set the bubble sizes?

A Use the raw values directly as sizes in plt.scatter.

B Use the logarithm (base 10) of the values as sizes without scaling.

C Apply a square root transformation to the values before passing as sizes.

D Normalize values between 0 and 1 and use them directly as sizes.

💡 Hint

Bubble area grows with the size parameter, so large raw values can cause huge bubbles.

Applying square root to values before sizing keeps bubble areas proportional to data but prevents very large bubbles, improving visual clarity.