Matplotlib.axes.Axes.matshow() in Python

# Implementation of matplotlib function
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import LogNorm
    
dx, dy = 0.015, 0.05
y, x = np.mgrid[slice(-4, 4 + dy, dy),
                slice(-4, 4 + dx, dx)]
z = (1 - x / 3. + x ** 5 + y ** 5) * 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.matshow(z, cmap ='Greens',
               vmin = z_min,
               vmax = z_max,
              extent =[x.min(),
                       x.max(), 
                       y.min(),
                       y.max()],
              interpolation ='nearest',
               origin ='lower')

fig.colorbar(c, ax = ax)
ax.set_title('matplotlib.axes.Axes.matshow() Examples\n')
plt.show()

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


def samplemat(dims):
    """Make a matrix with all zeros and increasing 
       elements on the diagonal"""

    aa = np.zeros(dims)
    for i in range(min(dims)):
        aa[i, i] = np.sin(i**3)**2 + i**3
    return aa


# Display matrix  
fig, ax = plt.subplots()
ax.matshow(samplemat((9, 9)), cmap ="Accent")

ax.set_title('matplotlib.axes.Axes.matshow() Examples\n')
plt.show()