Matplotlib.axes.Axes.pcolorfast() 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.pcolorfast() Function

The Axes.pcolorfast() function in axes module of matplotlib library is also used to create a pseudocolor plot with a non-regular rectangular grid.It has some limitations : supports only flat shading, lack of log scaling and lack of pyplot wrapper.

Syntax: Axes.pcolorfast(self, *args, alpha=None, norm=None, cmap=None, vmin=None, vmax=None, data=None, **kwargs)
pcolorfast([X, Y, ] C, **kwargs)

Parameters: This method accept the following parameters that are described below:

• C : This parameter contains the values in 2D array which are to be color-mapped.
• X, Y: These parameter are the coordinates of the quadrilateral corners.
• cmap : This parameter is a colormap instance or registered colormap name.
• norm : This parameter is the Normalize instance scales the data values to the canonical colormap range [0, 1] for mapping to colors
• vmin, vmax : These parameter are optional in nature and they are colorbar range.
• alpha : This parameter is a intensity of the color.
• snap : This parameter is used to snap the mesh to pixel boundaries.

Returns: This returns the following:

• image: This returns the image depend on AxesImage, PcolorImage and QuadMesh .

Below examples illustrate the matplotlib.axes.Axes.pcolorfast() function in matplotlib.axes:

Example-1:

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import LogNorm

Z = np.random.rand(30, 30)

fig, ax0 = plt.subplots()

ax0.pcolorfast(Z)

ax0.set_title('matplotlib.axes.Axes.pcolorfast() Examples')
plt.show()

Output:

Example-2:

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import LogNorm


dx, dy = 0.15, 0.05
y, x = np.mgrid[slice(-3, 3 + dy, dy), slice(-3, 3 + dx, dx)]
z = (1 - x / 2. + x ** 5 + y ** 3) * np.exp(-x ** 2 - y ** 2)


z = z[:-1, :-1]
z_min, z_max = -np.abs(z).max(), np.abs(z).max()

fig, ax = plt.subplots()

c = ax.pcolorfast(x, y, z, cmap ='Greens', vmin = z_min, vmax = z_max)
fig.colorbar(c, ax = ax)

ax.set_title('matplotlib.axes.Axes.pcolorfast() Examples')
plt.show()

Output: