Discrete colorbars in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a discrete colorbar with 5 colors.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

cmap = plt.cm.get_cmap('viridis', [1])
fig, ax = plt.subplots()
fig.colorbar(plt.cm.ScalarMappable(cmap=cmap), ax=ax, ticks=range(6))
plt.show()

Drag options to blanks, or click blank then click option'

A5

B10

C3

D7

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number that is too large or too small for the discrete colors.

Forgetting to pass the number of colors to get_cmap.

The get_cmap function's second argument sets the number of discrete colors. Here, 5 creates 5 discrete colors.

2fill in blank

medium

Complete the code to set the colorbar ticks correctly for 4 discrete colors.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

cmap = plt.cm.get_cmap('plasma', 4)
fig, ax = plt.subplots()
cb = fig.colorbar(plt.cm.ScalarMappable(cmap=cmap), ax=ax, ticks=[1])
plt.show()

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A[0, 1, 2, 3, 4]

B[1, 2, 3, 4]

C[0.25, 0.5, 0.75, 1]

D[0, 1, 2, 3]

Attempts:

3 left

💡 Hint

Common Mistakes

Using only 4 ticks for 4 colors, which misses the last boundary.

Using fractional ticks that don't align with color boundaries.

The ticks should cover all boundaries of the 4 discrete colors, so 5 ticks from 0 to 4 are needed.

3fill in blank

hard

Fix the error in the code to create a discrete colorbar with 3 colors.

Matplotlib

import matplotlib.pyplot as plt

cmap = plt.cm.get_cmap('coolwarm', 3)
fig, ax = plt.subplots()
cb = fig.colorbar(plt.cm.ScalarMappable(cmap=cmap), ax=ax, ticks=range([1]))
plt.show()

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A2

B3

C4

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using ticks range(3) which only gives 3 ticks for 3 colors.

Not setting the number of colors in get_cmap.

To create 3 discrete colors, the colormap must be created with 3 colors. The ticks should be from 0 to 3 to cover boundaries.

4fill in blank

hard

Fill both blanks to create a discrete colorbar with 6 colors and ticks from 0 to 6.

Matplotlib

import matplotlib.pyplot as plt

cmap = plt.cm.get_cmap('[1]', [2])
fig, ax = plt.subplots()
fig.colorbar(plt.cm.ScalarMappable(cmap=cmap), ax=ax, ticks=range(7))
plt.show()

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Atab10

B5

C6

Dviridis

Attempts:

3 left

💡 Hint

Common Mistakes

Using a continuous colormap name without specifying discrete colors.

Mismatch between number of colors and ticks.

The colormap name is 'tab10' which supports discrete colors well. The number of colors is 6 to match the ticks from 0 to 6.

5fill in blank

hard

Fill all three blanks to create a discrete colorbar with 4 colors, ticks from 0 to 4, and label the ticks with names.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

labels = ['Low', 'Medium', 'High', 'Very High']
cmap = plt.cm.get_cmap('[1]', [2])
fig, ax = plt.subplots()
cb = fig.colorbar(plt.cm.ScalarMappable(cmap=cmap), ax=ax, ticks=range([3]))
cb.ax.set_yticklabels(labels)
plt.show()

Drag options to blanks, or click blank then click option'

Acoolwarm

B4

C5

Dviridis

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong number of ticks for the number of colors.

Not matching labels count with colors.

The 'viridis' colormap is used with 4 discrete colors. Ticks go from 0 to 4 to cover boundaries for 4 colors. The labels correspond to the 4 color segments.