Colorblind-friendly palettes in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of color palette display code

What will be the output of this code snippet that uses a colorblind-friendly palette from matplotlib?

Matplotlib

import matplotlib.pyplot as plt
import seaborn as sns

palette = sns.color_palette("colorblind")
plt.figure(figsize=(6, 1))
plt.imshow([palette], aspect='auto')
plt.axis('off')
plt.show()

A A horizontal bar showing 8 distinct colors suitable for colorblind viewers

B A vertical bar showing 6 colors with random shades of blue

C A scatter plot with points colored in rainbow colors

D An error because 'colorblind' is not a valid palette name in seaborn

💡 Hint

Think about what sns.color_palette("colorblind") returns and how imshow displays colors.

The 'colorblind' palette in seaborn provides 8 distinct colors designed for colorblind accessibility. The code displays these colors as a horizontal bar using imshow.

❓ data_output

intermediate

Number of colors in a colorblind-friendly palette

How many colors are in the default matplotlib 'tab10' palette, which is also considered colorblind-friendly?

Matplotlib

import matplotlib.pyplot as plt
palette = plt.get_cmap('tab10')
num_colors = palette.N
print(num_colors)

A 10

B 8

C 12

D 6

💡 Hint

Check the attribute that gives the number of colors in the colormap object.

The 'tab10' colormap in matplotlib contains exactly 10 distinct colors, designed to be distinguishable and colorblind-friendly.

❓ visualization

advanced

Identify the colorblind-friendly palette used

Given this code, which colorblind-friendly palette is being used to plot the bars?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

values = [5, 7, 3, 8, 6]
colors = plt.get_cmap('tab20c').colors[:5]
plt.bar(range(5), values, color=colors)
plt.show()

A colorblind

B tab20c

C viridis

D Set1

💡 Hint

Look at the colormap name used in plt.get_cmap.

The code uses the 'tab20c' colormap from matplotlib, which is a colorblind-friendly palette with 20 colors in a cyclic pattern.

🔧 Debug

advanced

Why does this colorblind palette code raise an error?

This code raises an error. What is the cause?

Matplotlib

import matplotlib.pyplot as plt
import seaborn as sns

palette = sns.color_palette("colorblind", 10)
plt.figure(figsize=(6, 1))
plt.imshow([palette], aspect='auto')
plt.axis('off')
plt.show()

A plt.axis('off') is invalid syntax

B The 'colorblind' palette name is misspelled

C imshow cannot display color palettes

D The 'colorblind' palette only supports 8 colors, so requesting 10 causes an error

💡 Hint

Check the allowed number of colors for the 'colorblind' palette in seaborn.

The 'colorblind' palette in seaborn has a fixed set of 8 colors. Requesting 10 colors causes a ValueError.

🚀 Application

expert

Choosing a colorblind-friendly palette for a scatter plot

You want to plot a scatter plot with 7 categories, ensuring colors are distinguishable for colorblind viewers. Which palette should you choose from matplotlib?

A 'Pastel1' because it has soft colors but only 5 distinct colors

B 'viridis' because it is a sequential palette with smooth color changes

C 'tab10' because it has 10 distinct colors designed for colorblind accessibility

D 'Accent' because it has only 4 colors and is not colorblind-friendly

💡 Hint

Consider the number of categories and colorblind accessibility of palettes.

The 'tab10' palette has 10 distinct colors and is designed to be colorblind-friendly, making it suitable for 7 categories.