python中的Ellipse 95%置信区间

import numpy as np
from scipy.stats import chi2

center = [0, 0]  # 椭圆中心
width = 2  # 椭圆宽度
height = 1  # 椭圆高度
angle = np.pi/4  # 椭圆旋转角度

cov_matrix = np.array([[width**2, 0], [0, height**2]])
rotation_matrix = np.array([[np.cos(angle), -np.sin(angle)], [np.sin(angle), np.cos(angle)]])
cov_matrix = np.dot(rotation_matrix, np.dot(cov_matrix, rotation_matrix.T))

alpha = 0.05  # 置信水平
df = 2  # 自由度
chi2_value = chi2.ppf(1-alpha, df)
eigenvalues, eigenvectors = np.linalg.eig(cov_matrix)
radii = np.sqrt(chi2_value * eigenvalues)

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

fig, ax = plt.subplots()
ellipse = Ellipse(center, 2*radii[0], 2*radii[1], angle=np.degrees(angle), fill=False)
ax.add_patch(ellipse)
ax.set_xlim(center[0]-3, center[0]+3)
ax.set_ylim(center[1]-3, center[1]+3)
plt.gca().set_aspect('equal', adjustable='box')
plt.show()