Creating Color Maps

Introduction

In this lab, you will learn how to create color maps using Matplotlib. Color maps are useful when visualizing data, as they provide a way to represent numerical data through colors. Matplotlib provides a variety of built-in color maps, as well as the ability to create custom color maps.

VM Tips

After the VM startup is done, click the top left corner to switch to the Notebook tab to access Jupyter Notebook for practice.

Sometimes, you may need to wait a few seconds for Jupyter Notebook to finish loading. The validation of operations cannot be automated because of limitations in Jupyter Notebook.

If you face issues during learning, feel free to ask Labby. Provide feedback after the session, and we will promptly resolve the problem for you.

Skills Graph

Understanding Color Maps

A color map is a mapping between a range of numerical values and a range of colors. In Matplotlib, a color map is created using the matplotlib.colors module.

Creating a Simple Color Map

To create a simple color map, we can use the ListedColormap class from the matplotlib.colors module. This class takes a list of colors and creates a color map from them.

import matplotlib.colors as mcolors

## Define a list of colors
colors = ['red', 'green', 'blue']

## Create a ListedColormap object from the list of colors
cmap = mcolors.ListedColormap(colors)

Using Built-In Color Maps

Matplotlib provides a variety of built-in color maps that can be used to represent data. These color maps can be accessed using their names, which are listed in the matplotlib.cm module.

import matplotlib.pyplot as plt

## Create a plot using the 'viridis' color map
plt.imshow(data, cmap='viridis')
plt.colorbar()

Reversing Color Maps

Matplotlib provides the ability to reverse a color map by appending _r to the name of the color map.

import matplotlib.pyplot as plt

## Create a plot using the reversed 'viridis' color map
plt.imshow(data, cmap='viridis_r')
plt.colorbar()

Creating Custom Color Maps

Matplotlib also provides the ability to create custom color maps. This can be useful when the built-in color maps do not provide the desired representation of the data.

import matplotlib.colors as mcolors

## Define a list of colors and their corresponding values
colors = [(0, 'red'), (0.5, 'green'), (1, 'blue')]

## Create a LinearSegmentedColormap object from the list of colors
cmap = mcolors.LinearSegmentedColormap.from_list('my_cmap', colors)

Summary

In this lab, you learned how to create color maps using Matplotlib. You learned about the ListedColormap and LinearSegmentedColormap classes from the matplotlib.colors module, as well as the built-in color maps provided by Matplotlib. You also learned how to reverse a color map and create custom color maps.