Colorbar positioning in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the position of the colorbar in this plot?

Consider the following code that creates a heatmap and adds a colorbar. Where will the colorbar appear?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
data = np.random.rand(5,5)
cax = ax.imshow(data, cmap='viridis')
fig.colorbar(cax, ax=ax, orientation='vertical', fraction=0.046, pad=0.04)
plt.show()

A The colorbar is placed to the right of the heatmap, vertically aligned.

B The colorbar is placed below the heatmap, horizontally aligned.

C The colorbar is placed inside the heatmap, overlapping the data.

D The colorbar is placed to the left of the heatmap, vertically aligned.

💡 Hint

Check the orientation parameter and default colorbar placement.

The orientation='vertical' places the colorbar vertically. By default, it appears to the right of the main plot.

❓ data_output

intermediate

How many ticks are shown on the colorbar?

Given this code snippet, how many tick labels will the colorbar display?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
data = np.linspace(0, 1, 100).reshape(10,10)
cax = ax.imshow(data, cmap='plasma')
cbar = fig.colorbar(cax, ax=ax, ticks=[0, 0.25, 0.5, 0.75, 1])
plt.show()

A 10 tick labels

B No tick labels

C 4 tick labels

D 5 tick labels

💡 Hint

Look at the ticks argument passed to colorbar.

The ticks parameter explicitly sets 5 tick positions, so 5 labels appear on the colorbar.

❓ visualization

advanced

Identify the colorbar position from the plot layout

Below is a plot with a heatmap and a colorbar. The colorbar is positioned using ax_divider.append_axes. Where is the colorbar located?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.axes_grid1 import make_axes_locatable

fig, ax = plt.subplots()
data = np.random.rand(6,6)
cax = ax.imshow(data, cmap='coolwarm')
divider = make_axes_locatable(ax)
cbar_ax = divider.append_axes('top', size='5%', pad=0.1)
fig.colorbar(cax, cax=cbar_ax, orientation='horizontal')
plt.show()

A The colorbar is below the heatmap, horizontally aligned.

B The colorbar is above the heatmap, horizontally aligned.

C The colorbar is to the right of the heatmap, vertically aligned.

D The colorbar is inside the heatmap, overlapping the top-left corner.

💡 Hint

Check the append_axes position argument.

Using append_axes('top', ...) places the colorbar above the main axes.

🔧 Debug

advanced

Why does this colorbar not appear?

Examine the code below. The heatmap is shown but the colorbar does not appear. What is the cause?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
data = np.random.rand(4,4)
cax = ax.imshow(data, cmap='magma')
fig.colorbar(cax, orientation='horizontal', fraction=0.1, pad=0.05)
plt.show()

A The colorbar is too small and placed outside the figure area, so it is not visible.

B The colorbar orientation 'horizontal' is invalid and causes it not to render.

C The colorbar is not linked to the axes, so it does not display.

D The colormap 'magma' does not support colorbars.

💡 Hint

Check the fraction and pad parameters and figure size.

Using a very small fraction and pad can place the colorbar outside the visible figure area, making it invisible.

🚀 Application

expert

How to place two colorbars on opposite sides of a heatmap?

You want to create a heatmap with two colorbars: one on the left and one on the right side of the plot. Which code snippet correctly adds both colorbars?

Matplotlib

import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.axes_grid1 import make_axes_locatable

fig, ax = plt.subplots()
data = np.random.rand(8,8)
cax = ax.imshow(data, cmap='viridis')
divider = make_axes_locatable(ax)
# Add left colorbar
cbar_left_ax = divider.append_axes('left', size='5%', pad=0.1)
# Add right colorbar
cbar_right_ax = divider.append_axes('right', size='5%', pad=0.1)

# Add colorbars
fig.colorbar(cax, cax=cbar_left_ax)
fig.colorbar(cax, cax=cbar_right_ax)
plt.show()

A This code will raise an error because only one colorbar can be linked to one image.

B The colorbars will appear but both on the right side due to default behavior.

C This code correctly adds two colorbars on the left and right sides of the heatmap.

D The colorbars will overlap because the axes are not resized properly.

💡 Hint

Check how make_axes_locatable and append_axes work for multiple colorbars.

Using append_axes twice with different positions creates two separate axes for colorbars. Linking each colorbar to these axes displays both colorbars correctly.