How to Adjust the Position of a Matplotlib Colorbar?

A colorbar is a bar that has various colors in it and is placed along the sides of the Matplotlib chart. It is the legend for colors shown in the chart. By default, the position of the Matplotlib color bar is on the right side. The position of the Matplotlib color bar can be changed according to our choice by using the functions from Matplotlib AxesGrid Toolkit. The placing of inset axes is similar to that of legend, the position is modified by providing location options concerning the parent box.

Syntax: fig.colorbar(cm.ScalarMappable(norm=norm, cmap=cmap), ax=ax)

Attribute	Description
cax	Axes into which the colorbar will be drawn.
ax	Parent axes from which space for a new colorbar axes are stolen. If a list of axes is given they are resized to make room for colorbar axes.
colorbar	Use set_label to set the label to the colorbar
pad	relative subplot gap or fraction of original axes between colorbar and new image axes
LogNorm	Converting number arguments or color to RGBA
figsize	2-tuple of floats. Figure Dimension(width, height) in inches
add_subplot	Add an Axes to the figure as part of a subplot arrangement
add_axes	Present in figure module of matplotlib library used to add axes to figure
imshow	The convention used in image processing: the origin is in the top left corner.
pcolor	Creating a pseudocolor plot with a non-regular rectangular grid.

Installation of Matplotlib colorbar

To install the matplotlib colorbar directly execute the following command on Jupyter Notebook or Visual Studio Code to get the results, Matplotlib-colorbar package is installed in order to generate using the colorbar argument. Here, matplotlib.pyplot is used to create a colorbar in a simpler way.

pip install matplotlib-colorbar

Installation of Matplotlib Colorbar

Another way to create a colorbar using Matplotlib is by importing the matplotlib package and then creating the colorbar.

Python3

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import LogNorm

# specify dimensions of colorbar using random module
Z = np.random.rand(5, 20)

fig, ax0 = plt.subplots()
ax0.pcolor(Z)

ax0.set_title('Matplotlib-colorbar')
plt.show()

Output:

Example 1: Position of Matplotlib colorbar on Right Side

Generating a matplotlib chart where the colorbar is positioned on the right side of the chart.

Python3

# Import packages necessary to create colorbar
import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable

# make this example reproducible
np.random.seed(2)

#create chart
fig, ax = plt.subplots()
im = ax.imshow(np.random.rand(10,10))
ax.set_xlabel('x-axis label')

#add color bar
fig.colorbar(im)

plt.show()

Output:

Example 2: Position of Matplotlib colorbar on Left

Generating a Matplotlib chart where the colorbar is positioned on the left of the chart. Here, the axes locations are set manually and the colorbar is linked to the existing plot axis using the keyword ‘location’. Location argument is used on color bars that reference multiple axes in a list, if you put your one axis in a list then the argument can be used here. 

Python3

#import matplotlib.pyplot to create chart
import matplotlib.pyplot as plt
import numpy as np

#create subplot
fig = plt.figure()
ax = fig.add_subplot(111)
axp = ax.imshow(np.random.randint(0, 10,( 10, 10)))
ax.set_title('Colorbar on left')

#adding colorbar and its position
cb = plt.colorbar(axp ,ax = [ax], location = 'left')
plt.show()

Output:

This is a simple way to generate a colorbar and ensure it is on its own axis. Then the position of colorbar is specified using ‘cax’ parameter where axes are given for the color bar to be drawn.  

Python3

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

# make this example reproducible
np.random.seed(1)

# create chart
fig = plt.figure()
ax = fig.add_subplot(111)
axp = ax.imshow(np.random.randint(0, 10, (10, 10)))
ax.set_title('Colorbar on left')

# Adding the colorbar
cbaxes = fig.add_axes([0.1, 0.1, 0.03, 0.8])

# position for the colorbar
cb = plt.colorbar(axp, cax = cbaxes)
plt.show()

Output:

Example 3: Position of Matplotlib colorbar below the Chart

To position, the Matplotlib Colorbar below the chart then execute the following command, 

Python3

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

# make this reproducible
np.random.seed(2)

# create chart
fig, ax = plt.subplots()
im = ax.imshow(np.random.rand(10,10))
ax.set_xlabel('x-axis label')

# add color bar below chart
divider = make_axes_locatable(ax)
cax = divider.new_vertical(size='5%', pad=0.6, pack_start = True)
fig.add_axes(cax)
fig.colorbar(im, cax = cax, orientation = 'horizontal')

plt.show()

Output:

Pad argument creates padding between the x-axis of the chart and colorbar. Higher the value for the pad, the colorbar is away from the x-axis. To move colorbar relative to the subplot use the pad argument to fig.colorbar.

Python3

# import matplotlib packages
import matplotlib.pyplot as plt
import numpy as np; np.random.seed(1)


# create chart
fig, ax = plt.subplots(figsize=(4,4))
im = ax.imshow(np.random.rand(11,16))
ax.set_xlabel("x label")

# pad argument to set colorbar away from x-axis
fig.colorbar(im, orientation="horizontal", pad = 0.4)
plt.show()

Output:

 Use the instance of make_axes_locatable to divide axes and create new axes which are aligned to the image plot. Pad argument will allow setting space between two axes: 

Python3

# import matplotlib packages
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
import numpy as np; np.random.seed(1)

fig, ax = plt.subplots(figsize = (4,4))
im = ax.imshow(np.random.rand(11,16))
ax.set_xlabel("x label")

# instance is used to divide axes
divider = make_axes_locatable(ax)
cax = divider.new_vertical(size = "5%",
                           pad = 0.7,
                           pack_start = True)
fig.add_axes(cax)

# creating colorbar
fig.colorbar(im, cax = cax, orientation = "horizontal")

plt.show()

Output:

Example 4: Position of Colorbar above Chart

To position, the Matplotlib Colorbar below the chart then execute the following command,

Python3

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

# make this example reproducible
np.random.seed(1)

# create chart
fig, ax = plt.subplots()
im = ax.imshow(np.random.rand(15, 15))
ax.set_xlabel('x-axis label')
ax.set_title('Colorbar above chart')

# add color bar below chart
divider = make_axes_locatable(ax)
cax = divider.new_vertical(size = '5%', pad = 0.5)
fig.add_axes(cax)
fig.colorbar(im, cax = cax, orientation = 'horizontal')

plt.show()

Output: