matplotlib example wall-crossing (snippet)

Python matplotlib example 'wall-crossing'

Modules used in program:

• import matplotlib.pyplot as plt
• import numpy as np

python wall-crossing

Python matplotlib example: wall-crossing

# plt.contour assumes there are lines between theta = 0 and theta = 2*np.pi

import numpy as np
import matplotlib.pyplot as plt
#%matplotlib inline
plt.rcParams['figure.figsize']=7,7

# rm foo*.png
# convert foo*.png foo.gif

dt = 0.01
L = 5
t  = np.arange(-L,L+dt, dt)
z = t[...,None]+1j*t[None,...]

N = 20

PP = np.polyval(P,z)

for k in np.arange(N):
    print("%02d" %(k))

    w = np.log(np.exp(2j*np.pi*(k*1.0/N))*PP)

    ds = 0.05
    plt.contour(t, t, w.imag%(2*np.pi), levels = 2*np.pi*np.arange(0,1, ds), colors=('#505050','#707070'), linewidth=1)
    plt.contour(t, t, w.imag%(2*np.pi), levels = 2*np.pi*np.arange(0,1, 0.5), colors='w', linewidth=50)
    plt.contour(t, t, w.real, levels = np.arange(0,5,0.1)**1, colors=('#A2D426','#6B6CED'))

    L = 3
    plt.xlim([-L,L])
    plt.ylim([-L,L])
    #plt.show()

    plt.savefig('/home/jdm/Documents/math/foo-%02d.png'%(k))
    plt.clf()

Python links

• Learn Python: https://pythonbasics.org/
• Python Tutorial: https://pythonprogramminglanguage.com