Creating a Confidence Ellipses in a sccatterplot using matplotlib

Question

How to creating a Confidence Ellipses in a sccatterplot using matplotlib?

The following code works until creating scatter plot. Then, does anyone familiar with putti

Answer 1

After giving the accepted answer a go, I found that it doesn't choose the quadrant correctly when calculating theta, as it relies on np.arccos:

Taking a look at the 'possible duplicate' and Joe Kington's solution on github, I watered his code down to this:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.patches import Ellipse

def eigsorted(cov):
    vals, vecs = np.linalg.eigh(cov)
    order = vals.argsort()[::-1]
    return vals[order], vecs[:,order]

x = [5,7,11,15,16,17,18]
y = [25, 18, 17, 9, 8, 5, 8]

nstd = 2
ax = plt.subplot(111)

cov = np.cov(x, y)
vals, vecs = eigsorted(cov)
theta = np.degrees(np.arctan2(*vecs[:,0][::-1]))
w, h = 2 * nstd * np.sqrt(vals)
ell = Ellipse(xy=(np.mean(x), np.mean(y)),
              width=w, height=h,
              angle=theta, color='black')
ell.set_facecolor('none')
ax.add_artist(ell)
plt.scatter(x, y)
plt.show()