from matplotlib.patches import Rectangle

import matplotlib.pyplot as plt
import numpy as np

def save_plot(filename, bound, eps, delta):
	f, ax = plt.subplots()

	ax.axhline(color="black")
	ax.axvline(color="black")

	ax.set_xlim(-bound,bound)
	ax.set_ylim(-2,2)

	ax.add_patch(
		Rectangle((-delta,-eps), 2*delta, 2*eps, edgecolor="black",
		          alpha=0.6, linestyle="solid", facecolor="#dddddd", lw=1.5))

	ax.plot([-bound,0],[-1,-1], color="blue")
	ax.plot([0,bound],[1,1], color="blue")

	ax.plot([-delta,0],[-1,-1], color="red", lw=2)
	ax.plot([0,delta],[1,1], color="red", lw=2)

	ax.plot([0,0],[1,-1], "o", color="white")
	ax.plot([0], [0], "o", color="green")

	plt.savefig(filename)

save_plot("Illustration of discontinuity with sgn(x).svg", bound=2, eps=0.5, delta=0.5)
save_plot("Illustration of discontinuity with sgn(x) (version 2).svg", bound=2, eps=0.5, delta=1)