Matplotlib - Paths

A path is a route (track) that guides movement from one place to another. It can be physical, like a trail or road, or abstract, like a series of steps to achieve a goal. Paths provide direction and help us to navigate through spaces. They signify a way to reach a destination.

Paths

Paths in Matplotlib

In Matplotlib, paths are fundamental objects used to draw shapes and lines on plots. A path consists of a series of connected points, known as vertices or nodes, along with instructions on how to connect these points to form shapes like lines, curves, or polygons.

You can create a path in Matplotlib using the "Path" class. These paths can be used to create various types of plots such as lines, curves, polygons, and even custom shapes. Paths provide a way to define the appearance of objects in plots, allowing you to control their size, position, and style.

Let’s start by drawing a basic straight line path.

Straight Line Path

In Matplotlib, a straight line path refers to a basic geometric element consisting of two points connected by a straight line. This path is created by specifying the coordinates of the starting point (often called the "origin") and the ending point of the line. Matplotlib then draws a straight line between these two points, forming the path.

Example

In the following example, we are creating a straight line path using the Path class in Matplotlib. We define two vertices representing the starting and ending points of the line. Additionally, we specify the path codes to indicate that the path moves to the first vertex and then creates a line to the second vertex. By constructing the path using these vertices and codes, we achieve the representation of a straight line −

import matplotlib.pyplot as plt
from matplotlib.path import Path
import matplotlib.patches as patches

# Defining the vertices for the straight line path
verts = [
   # Starting point
   (0, 0),
   # Ending point
   (1, 1)   
]

# Defining the codes for the straight line path
codes = [Path.MOVETO, Path.LINETO]

# Creating the straight line path
path = Path(verts, codes)

# Plotting the path
fig, ax = plt.subplots()
patch = patches.PathPatch(path, facecolor='none', lw=2)
ax.add_patch(patch)
ax.set_title('Straight Line Path')
ax.set_xlim(0, 1)
ax.set_ylim(0, 1)
ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
ax.grid(True)
plt.show()

Output

Following is the output of the above code −

Straight Line Path

Circle Path

In Matplotlib, a circle path represents a circular shape drawn on a plot. It is created by specifying the center point of the circle and its radius. Matplotlib then generates a series of points around the circumference of the circle, connecting them to form a closed path.

Example

In here, we are creating a circular path using the Path class in Matplotlib. We generate a sequence of vertices along the circumference of a circle by defining angles uniformly spaced around the unit circle. Using trigonometric functions, we compute the coordinates of these vertices. Subsequently, we define the path codes to connect these vertices with lines −

import matplotlib.pyplot as plt
from matplotlib.path import Path
import matplotlib.patches as patches
import numpy as np

# Defining the angles for the circle path
theta = np.linspace(0, 2*np.pi, 100)

# Defining the vertices for the circle path
verts = np.column_stack([np.cos(theta), np.sin(theta)])

# Definng the codes for the circle path
codes = [Path.MOVETO] + [Path.LINETO] * (len(verts) - 1)

# Creating the circle path
path = Path(verts, codes)

# Plotting the path
fig, ax = plt.subplots()
patch = patches.PathPatch(path, facecolor='none', lw=2)
ax.add_patch(patch)
ax.set_title('Circle Path')
ax.set_xlim(-1.1, 1.1)
ax.set_ylim(-1.1, 1.1)
ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
ax.grid(True)
plt.show()

Output

On executing the above code we will get the following output −

Circle Path

Bezier Curve Path

In Matplotlib, a Bezier curve path is a smooth, curved line created using control points to define its shape.

To construct a Bezier curve, you specify a series of control points that guide the curve's path. These control points determine the curve's direction and shape, allowing you to create smooth, flowing shapes. Matplotlib then generates the curve by connecting the dots these control points.

Example

Now, we are creating a Bezier curve path in Matplotlib using the Path class. We specify the control points that define the shape of the Bezier curve. Additionally, we define the path codes to indicate the type of curve segments between consecutive control points. By constructing the path with these control points and codes, we create a smooth Bezier curve −

import matplotlib.pyplot as plt
from matplotlib.path import Path
import matplotlib.patches as patches

# Defining the control points for the Bezier curve
verts = [
   (0.1, 0.1),
   (0.2, 0.8),
   (0.8, 0.8),
   (0.9, 0.1),
]

# Defining the codes for the Bezier curve path
codes = [Path.MOVETO, Path.CURVE4, Path.CURVE4, Path.CURVE4]

# Creating the Bezier curve path
path = Path(verts, codes)

# Plotting the path
fig, ax = plt.subplots()
patch = patches.PathPatch(path, facecolor='none', lw=2)
ax.add_patch(patch)
ax.set_title('Bezier Curve Path')
ax.set_xlim(0, 1)
ax.set_ylim(0, 1)
ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
ax.grid(True)
plt.show()

Output

After executing the above code, we get the following output −

Bezier Curve Path

Polygon Path

In Matplotlib, a polygon path represents a closed shape with multiple straight sides, similar to a geometric polygon. This shape is created by specifying the coordinates of its vertices, or corner points, in a specific order. Matplotlib then connects these points sequentially to form the edges of the polygon and closes the path by connecting the last point to the first.

Polygon paths are versatile elements used to represent various shapes, such as triangles, rectangles, pentagons, or any other multi-sided figures. They can be filled with color to represent areas or used as outlines to highlight specific regions in plots.

Example

In this example, we create a polygonal path using the Path class in Matplotlib. We define the vertices of the polygon, representing the corners of the polygonal shape. Additionally, we specify the path codes to connect these vertices and close the polygon. By constructing the path with the vertices and codes, we form a closed polygonal shape −

import matplotlib.pyplot as plt
from matplotlib.path import Path
import matplotlib.patches as patches

# Defining the vertices for the polygon
verts = [
   (0.1, 0.1),
   (0.5, 0.9),
   (0.9, 0.1),
   # Closing the polygon
   (0.1, 0.1)  
]

# Defining the codes for the polygon path
codes = [Path.MOVETO, Path.LINETO, Path.LINETO, Path.CLOSEPOLY]

# Creating the polygon path
path = Path(verts, codes)

# Plotting the path
fig, ax = plt.subplots()
patch = patches.PathPatch(path, facecolor='none', lw=2)
ax.add_patch(patch)
ax.set_title('Polygon Path')
ax.set_xlim(0, 1)
ax.set_ylim(0, 1)
ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
ax.grid(True)
plt.show()

Output

On executing the above code we will get the following output −

Polygon Path
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