Matplotlib.axes.Axes.tricontour() in Python

Matplotlib is a library in Python and it is numerical – mathematical extension for NumPy library. The Axes Class contains most of the figure elements: Axis, Tick, Line2D, Text, Polygon, etc., and sets the coordinate system. And the instances of Axes supports callbacks through a callbacks attribute.

matplotlib.axes.Axes.tricontour() Function

The Axes.tricontour() function in axes module of matplotlib library is also used to draw contours on an unstructured triangular grid.

Syntax:

Axes.tricontour(ax, *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.

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.axes.Axes.tricontour() function in matplotlib.axes: 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, 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, 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(1.5 * x) * np.cos(1.5 * y)

fig, axs = plt.subplots()
t = axs.tricontourf(triang, z)
axs.tricontour(triang, z, colors ='white')
fig.colorbar(t)

axs.set_title('matplotlib.axes.Axes.tricontour() Example')
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 = 26
n_radii = 10
min_radius = 0.35
radii = np.linspace(min_radius, 0.95, n_radii)

angles = np.linspace(0, 2 * 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) * np.cos(3 * 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)

fig1, ax1 = plt.subplots()
ax1.set_aspect('equal')
tcf = ax1.tricontourf(triang, z)
fig1.colorbar(tcf)
ax1.tricontour(triang, z, colors ='g')
ax1.set_title('matplotlib.axes.Axes.tricontour() Example')
plt.show()

Output: