Matplotlib Ellipse Collection

Introduction

Matplotlib is a powerful data visualization library in Python. In this lab, we will explore the use of EllipseCollection to draw a collection of ellipses.

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Skills Graph

Import necessary libraries

We will start by importing the necessary libraries.

import matplotlib.pyplot as plt
import numpy as np

from matplotlib.collections import EllipseCollection

Create data for ellipses

We create data for our ellipses in the form of arrays of x-coordinates, y-coordinates, width, height and angle.

x = np.arange(10)
y = np.arange(15)
X, Y = np.meshgrid(x, y)

XY = np.column_stack((X.ravel(), Y.ravel()))

ww = X / 10.0
hh = Y / 15.0
aa = X * 9

Create Ellipse Collection

We create an EllipseCollection with the above data and specify the units to be 'x' and the offsets to be XY.

fig, ax = plt.subplots()

ec = EllipseCollection(ww, hh, aa, units='x', offsets=XY,
                       offset_transform=ax.transData)

Set the color of ellipses

We set the color of each ellipse in the EllipseCollection based on the sum of its x and y coordinate.

ec.set_array((X + Y).ravel())

Add collection to the plot

We add the EllipseCollection to the plot.

ax.add_collection(ec)
ax.autoscale_view()
ax.set_xlabel('X')
ax.set_ylabel('y')
cbar = plt.colorbar(ec)
cbar.set_label('X+Y')
plt.show()

Summary

In this lab, we learned how to use EllipseCollection to draw a collection of ellipses in Matplotlib. We also learned how to set the color of each ellipse based on its x and y coordinate.