Matplotlib.pyplot.triplot() in python

Last Updated : 19 Apr, 2020

Matplotlib is a library in Python and it is numerical - mathematical extension for NumPy library. Pyplot is a state-based interface to a Matplotlib module which provides a MATLAB-like interface. There are various plots which can be used in Pyplot are Line Plot, Contour, Histogram, Scatter, 3D Plot, etc.

matplotlib.pyplot.triplot() Function:

The triplot() function in pyplot module of matplotlib library is used to draw a unstructured triangular grid as lines and/or markers.

Syntax: matplotlib.pyplot.triplot(*args, **kwargs) Parameters: This method accept the following parameters that are described below:

x, y: These parameter are the x and y coordinates of the data which is to be plot.

triangulation: This parameter is a matplotlib.tri.Triangulation object.

**kwargs: This parameter is Text properties that is used to control the appearance of the labels.
All remaining args and kwargs are the same as for matplotlib.pyplot.plot().
Returns: This returns the list of 2 Line2D containing following:

The lines plotted for triangles edges.

The markers plotted for triangles nodes

Below examples illustrate the matplotlib.pyplot.triplot() function in matplotlib.pyplot: Example 1:

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import matplotlib.tri as mtri
import numpy as np
 
# Create triangulation.
x = np.asarray([0, 1, 2, 3, 0.5, 1.5,
                2.5, 1, 2, 1.5])

y = np.asarray([0, 0, 0, 0, 1.0,
                1.0, 1.0, 2, 2, 3.0])

triangles = [[0, 1, 4], [1, 2, 5], 
             [2, 3, 6], [1, 5, 4], 
             [2, 6, 5], [4, 5, 7],
             [5, 6, 8], [5, 8, 7],
             [7, 8, 9]]

triang = mtri.Triangulation(x, y, triangles)
z = np.cos(1.5 * x) * np.cos(1.5 * y)
 
plt.tricontourf(triang, z)
plt.triplot(triang, 'go-')
 
plt.title('matplotlib.pyplot.triplot() Example')
plt.show()

Output:

Example 2:

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import matplotlib.tri as tri
import numpy as np
 
n_angles = 24
n_radii = 9
min_radius = 0.5
radii = np.linspace(min_radius, 0.9,
                    n_radii)
 
angles = np.linspace(0, 3 * np.pi, n_angles, 
                     endpoint = False)

angles = np.repeat(angles[..., np.newaxis], 
                   n_radii, axis = 1)

angles[:, 1::2] += np.pi / n_angles
 
x = (radii * np.cos(angles)).flatten()
y = (radii * np.sin(angles)).flatten()
triang = tri.Triangulation(x, y)
 
triang.set_mask(np.hypot(x[triang.triangles].mean(axis = 1),
                         y[triang.triangles].mean(axis = 1))
                < min_radius)

plt.triplot(triang, 'go-', lw = 1)
plt.title('matplotlib.pyplot.triplot() Example')
plt.show()