Creating Matplotlib PathPatch Objects

Introduction

Matplotlib is a Python library that allows the user to create different types of charts and graphs. It is used in data visualization and data analysis. In this lab, we will learn how to create a PathPatch object using Matplotlib's API.

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Skills Graph

Import Libraries

We need to import the required libraries for this lab.

import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import matplotlib.path as mpath

Define Path Data

We define the path data in this step. Path data is a sequence of tuples that specify the vertices and codes of the path. We use the mpath.Path class to create a Path object from this data.

Path = mpath.Path
path_data = [
    (Path.MOVETO, (1.58, -2.57)),
    (Path.CURVE4, (0.35, -1.1)),
    (Path.CURVE4, (-1.75, 2.0)),
    (Path.CURVE4, (0.375, 2.0)),
    (Path.LINETO, (0.85, 1.15)),
    (Path.CURVE4, (2.2, 3.2)),
    (Path.CURVE4, (3, 0.05)),
    (Path.CURVE4, (2.0, -0.5)),
    (Path.CLOSEPOLY, (1.58, -2.57)),
    ]
codes, verts = zip(*path_data)
path = mpath.Path(verts, codes)

Create PathPatch Object

In this step, we create a PathPatch object using the path object that we created in the previous step. This object is used to fill the area enclosed by the path. We can also set the color and transparency of the patch.

patch = mpatches.PathPatch(path, facecolor='r', alpha=0.5)

Add PathPatch to Plot

Now, we add the patch object to the plot using the add_patch method of the axes object.

fig, ax = plt.subplots()
ax.add_patch(patch)

Plot Control Points and Connecting Lines

In this step, we plot the control points and connecting lines of the path using the plot method of the axes object.

x, y = zip(*path.vertices)
line, = ax.plot(x, y, 'go-')

Customize Plot

Finally, we customize the plot by adding a grid and equalizing the axes.

ax.grid()
ax.axis('equal')
plt.show()

Summary

In this lab, we learned how to create a PathPatch object using Matplotlib's API. We defined the path data, created a Path object, and used it to create a PathPatch object that we added to the plot. We also plotted the control points and connecting lines of the path and customized the plot by adding a grid and equalizing the axes.