Matplotlib.pyplot.tricontourf() in Python

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.  

Matplotlib.pyplot.tricontourf()

The tricontourf() function in pyplot module of matplotlib library is used to draw contours on an unstructured triangular grid.

Syntax:  matplotlib.pyplot.tricontourf(\*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.
• Z: This parameter is the array of values to contour, one per point in the triangulation.
• **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

Note: tricontourf-only keyword arguments is antialiased which is a bool enable antialiasing which used in contours on an unstructured triangular grid.

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

Python3

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

triang = mtri.Triangulation(x, y, triangles)
z = np.cos(2.5 * x*x) + np.sin(2.5 * x*x)

t = plt.tricontourf(triang, z)

plt.title('matplotlib.pyplot.tricontourf() Example\n',
          fontsize=14, fontweight='bold')

plt.show()

Output:

Example 2:

Python3

#Implementation of matplotlib function
import matplotlib.pyplot as plt
import matplotlib.tri as tri
import numpy as np


n_angles = 60
n_radii = 10
min_radius = 0.35
radii = np.linspace(min_radius, 0.95, n_radii)

angles = np.linspace(0, np.pi, n_angles, endpoint = False)
angles = np.repeat(angles[..., np.newaxis], n_radii, axis = 1)
angles[:, 1::2] += np.pi / n_angles

x = (10 * radii * np.cos(angles)).flatten()
y = (10 * radii * np.sin(angles)).flatten()
z = (np.cos(4*(radii)**2) * np.sin((angles)**2)).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)

tcf = plt.tricontourf(triang, z)

plt.colorbar(tcf)
plt.title('matplotlib.pyplot.tricontourf() Example\n',
          fontsize=14, fontweight='bold')

plt.show()

Output: