# units example code: ellipse_with_units.pyΒΆ

```"""
Compare the ellipse generated with arcs versus a polygonal approximation
"""
from basic_units import cm
import numpy as np
from matplotlib import patches
import matplotlib.pyplot as plt

xcenter, ycenter = 0.38*cm, 0.52*cm
#xcenter, ycenter = 0., 0.
width, height = 1e-1*cm, 3e-1*cm
angle = -30

theta = np.arange(0.0, 360.0, 1.0)*np.pi/180.0
x = 0.5 * width * np.cos(theta)
y = 0.5 * height * np.sin(theta)

rtheta = angle*np.pi/180.
R = np.array([
[np.cos(rtheta),  -np.sin(rtheta)],
[np.sin(rtheta), np.cos(rtheta)],
])

x, y = np.dot(R, np.array([x, y]))
x += xcenter
y += ycenter

fig = plt.figure()
ax.fill(x, y, alpha=0.2, facecolor='yellow', edgecolor='yellow', linewidth=1, zorder=1)

e1 = patches.Ellipse((xcenter, ycenter), width, height,
angle=angle, linewidth=2, fill=False, zorder=2)

ax.fill(x, y, alpha=0.2, facecolor='green', edgecolor='green', zorder=1)
e2 = patches.Ellipse((xcenter, ycenter), width, height,
angle=angle, linewidth=2, fill=False, zorder=2)

#fig.savefig('ellipse_compare.png')
fig.savefig('ellipse_compare')

fig = plt.figure()
ax.fill(x, y, alpha=0.2, facecolor='yellow', edgecolor='yellow', linewidth=1, zorder=1)

e1 = patches.Arc((xcenter, ycenter), width, height,
angle=angle, linewidth=2, fill=False, zorder=2)

ax.fill(x, y, alpha=0.2, facecolor='green', edgecolor='green', zorder=1)
e2 = patches.Arc((xcenter, ycenter), width, height,
angle=angle, linewidth=2, fill=False, zorder=2)