Python で線形補間を使用してプロット上で正確なゼロおよびゼロ以外の切片を見つける方法

<code class="python">import numpy as np

def find_roots(x, y):
    s = np.abs(np.diff(np.sign(y))).astype(bool)
    return x[:-1][s] + np.diff(x)[s]/(np.abs(y[1:][s]/y[:-1][s])+1)

x = .4+np.sort(np.random.rand(750))*3.5
y = (x-4)*np.cos(x*9.)*np.cos(x*6+0.05)+0.1

z = find_roots(x,y)

plt.plot(x,y)
plt.plot(z, np.zeros(len(z)), marker="o", ls="", ms=4)</code>

<code class="python">z = find_roots(x,y-y0)</code>

<code class="python">y2 = (x - 2) * np.cos(x * 8.) * np.cos(x * 5 + 0.03) + 0.3

z = find_roots(x,y2-y1)

plt.plot(x,y1)
plt.plot(x,y2, color="C2")
plt.plot(z, np.interp(z, x, y1), marker="o", ls="", ms=4, color="C1")</code>