Creating Artists with Units

Introduction

In this lab, you will learn how to create artists with units in Matplotlib. You will create different types of artists, such as a line, text, and patch, and add them to a plot. You will also set the units for the x and y axes, and learn how to convert units to scalars.

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

Import Libraries

First, you need to import the necessary libraries. You will use matplotlib.pyplot for creating the plot, numpy for generating random data, and matplotlib.collections, matplotlib.lines, matplotlib.patches, and matplotlib.text for creating different types of artists.

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.collections as collections
import matplotlib.lines as lines
import matplotlib.patches as patches
import matplotlib.text as text

Create the Figure and Axis

Next, you need to create the figure and axis objects. The figure object is the top-level container for all the plot elements, while the axis object represents the x and y axes of the plot.

fig, ax = plt.subplots()

Set Units for the Axes

To use units for the x and y axes, you need to set the units for each axis using the set_units method. In this example, you will use centimeters as the unit.

ax.xaxis.set_units('cm')
ax.yaxis.set_units('cm')

Generate Random Data

To create the line artist, you need to generate some random data. You will use numpy.random to generate 2 sets of x and y coordinates for the line.

x = np.array([0, 1.5])
y = np.array([0, 2.5])

Create a Line Artist

Now, you can create the line artist using the Line2D class from matplotlib.lines. You can specify the x and y coordinates, line width, color, and axis object as arguments.

line = lines.Line2D(x, y, lw=2, color='black', axes=ax)

Add the Artist to the Plot

To add the line artist to the plot, you need to call the add_line method of the axis object and pass the line artist as an argument.

ax.add_line(line)

Create a Text Artist

Next, you will create a text artist using the Text class from matplotlib.text. You can specify the x and y coordinates, text label, horizontal and vertical alignment, and axis object as arguments.

t = text.Text(3, 2.5, 'text label', ha='left', va='bottom', axes=ax)

Add the Artist to the Plot

To add the text artist to the plot, you need to call the add_artist method of the axis object and pass the text artist as an argument.

ax.add_artist(t)

Set the Limits of the Plot

To set the limits of the plot, you need to call the set_xlim and set_ylim methods of the axis object and pass the minimum and maximum values for each axis.

ax.set_xlim(-1, 10)
ax.set_ylim(-1, 10)

Display the Plot

Finally, you can display the plot using the show method of pyplot.

plt.show()

Summary

In this lab, you learned how to create artists with units in Matplotlib. You learned how to set the units for the x and y axes, generate random data, create line and text artists, and add them to a plot. You also learned how to set the limits of the plot and display it.