Creating Color Maps with Matplotlib

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

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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.

Creating Color Maps