butterfly_curves.py

"""
Plot multiple butterfly curves.
"""

import numpy as np
import matplotlib.pyplot as plt

def curve(turns, npts):
    t = np.linspace(0, 2*turns*np.pi, npts)
    x = np.sin(t)*(np.exp(np.cos(t))- 2*np.cos(4*t) - np.sin(t/12)**5)
    y = np.cos(t)*(np.exp(np.cos(t))- 2*np.cos(4*t) - np.sin(t/12)**5)
    return x, y

inc = 0.2
ncur = 4
x, y = curve(10, 10000)
for k in range(ncur):
    plt.plot((1+k*inc)*x, (1+k*inc)*y, zorder=ncur+3-k)

plt.axis('tight')
plt.axis('off')
plt.savefig('gift.svg')
plt.savefig('gift.png', dpi=600)