Matplotlib - contour(), contourf()

https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.contour.html

https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.contourf.html

https://matplotlib.org/stable/api/_as_gen/matplotlib.pyplot.colorbar.html

https://numpy.org/doc/stable/reference/generated/numpy.meshgrid.html

CONTOUR AND CONTOURF

'contour' and 'contourf' draw contour lines and filled contours, respectively.

# matplotlib.pyplot.contour(*args, data=None, **kwargs)
# Call signature:
# contourf([X, Y,] Z, [levels], **kwargs)
# X, Y : array-like, the coordinates of the values in Z.
# Z : array-like, the height values over which the contour is drawn.

# matplotlib.pyplot.contourf(*args, data=None, **kwargs)
# Call signature:
# contourf([X, Y,] Z, [levels], **kwargs)

# contour1.py
import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(-5,5,101)
y = np.linspace(-5,5,101)
xx, yy = np.meshgrid(x, y)
#print(xx.shape)   # (101, 101)
#print(yy.shape)   # (101, 101)
zz = np.sqrt(xx**2 + yy**2)   # numpy functions
#print(zz.shape)   # (101, 101)

plt.contourf(xx, yy, zz)
#plt.contourf(x, y, zz)   # it works
#plt.contourf(zz)   # indices are used

#plt.contour(xx, yy, zz)
#plt.contour(x, y, zz)   # it works
#plt.contour(zz)   # indices are used

plt.axis('scaled')
plt.colorbar()
plt.title("contour or contourf")
plt.xlabel("x")
plt.ylabel("y")
plt.show()