Draw implicit function in python
Implicit function drawing
An implicit function is $ f (x, y) = 0 $, which is difficult to transform into an explicit shape.
Yen $ x ^ 2 + y ^ 2-1 = 0 $ is a typical example.
It's not impossible to transform it, but it's not very smart when drawing graphs because it requires case classification.
In such cases, contour is convenient.
python
import matplotlib.pyplot as plt
import numpy as np
delta = 0.025
xrange = np.arange(-2, 2, delta)
yrange = np.arange(-2, 2, delta)
X, Y = np.meshgrid(xrange,yrange)
#Axis settings
plt.axis([-2, 2, -2, 2])
plt.gca().set_aspect('equal', adjustable='box')
#drawing
Z=X**2+Y**2-1
plt.contour(X, Y, Z, [0])
plt.show()
Plt.contour (X, Y, Z, [0]) in the code draws contour lines with Z = 0.
If you specify [-1,0,1], contour lines will be added. It's smart.
Other method
It's pretty short, but I feel like I'm just painting $-\ epsilon <f (x, y) <\ epsilon $.
python
from sympy import *
x, y = symbols("x y")
Z=x**2+y**2-1
plot_implicit(Z, (x, -2, 2), (y, -2, 2))
Execution result
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