Colorbar configuration in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this colorbar orientation code?

Consider this matplotlib code that creates a colorbar with a specific orientation. What will be the orientation of the colorbar?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
img = ax.imshow(np.random.rand(5,5))
cbar = fig.colorbar(img, orientation='horizontal')
print(cbar.orientation)

A none

B diagonal

C vertical

D horizontal

💡 Hint

Check the orientation parameter passed to fig.colorbar().

The orientation parameter controls the direction of the colorbar. Here it is set to horizontal, so the colorbar orientation is horizontal.

❓ data_output

intermediate

How many ticks are shown on this colorbar?

This code creates a colorbar with 5 ticks. How many tick labels will be shown on the colorbar?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
img = ax.imshow(np.random.rand(10,10))
cbar = fig.colorbar(img, ticks=[0, 0.25, 0.5, 0.75, 1])
print(len(cbar.ax.get_yticklabels()))

A 4

B 6

C 5

D 0

💡 Hint

The number of tick labels matches the number of ticks specified in the ticks list.

Exactly 5 ticks are specified with ticks=[0, 0.25, 0.5, 0.75, 1], so there are 5 tick labels shown on the colorbar.

🔧 Debug

advanced

Why does this colorbar code raise an error?

Examine the code below. It raises an error when run. What is the cause?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
img = ax.imshow(np.random.rand(5,5))
cbar = fig.colorbar(img, orientation='sideways')

A ValueError because 'sideways' is not a valid orientation

B SyntaxError due to invalid orientation value

C TypeError because colorbar expects a string but got None

D No error, code runs fine

💡 Hint

Check the allowed values for the orientation parameter.

The orientation parameter only accepts 'vertical' or 'horizontal'. 'sideways' is invalid and causes a ValueError.

❓ visualization

advanced

Which option produces a colorbar with ticks inside the plot area?

Given the following code snippet, which option correctly sets the colorbar ticks to appear inside the plot area?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
img = ax.imshow(np.random.rand(5,5))
cbar = fig.colorbar(img)
# Set ticks inside here

A cbar.ax.tick_params(direction='in')

B cbar.set_ticks_position('none')

C cbar.set_ticks_position('outside')

D cbar.ax.tick_params(direction='out')

💡 Hint

Look for the parameter controlling tick direction.

Using tick_params(direction='in') sets the ticks to point inside the plot area.

🚀 Application

expert

How to create a colorbar with a custom label and fixed size?

You want to add a vertical colorbar to your plot with the label 'Intensity' and fix its width to 0.1 of the figure width. Which code snippet achieves this?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
img = ax.imshow(np.random.rand(10,10))

A cbar = fig.colorbar(img, label='Intensity', fraction=0.1)

B

cbar = fig.colorbar(img, fraction=0.1)
cbar.set_label('Intensity')

C

cbar = fig.colorbar(img)
cbar.set_label('Intensity')
cbar.ax.set_aspect(0.1)

D

cbar = fig.colorbar(img, fraction=0.1, orientation='horizontal')
cbar.set_label('Intensity')

💡 Hint

Check the fraction parameter for size and use set_label for labeling.

The fraction parameter controls the fraction of the original axes to use for the colorbar width. The label is set with set_label.