old_contents: # External Packages
  import matplotlib.pyplot as plt
  import matplotlib.animation as anim
  import numpy as np
  
  # Custom Packages
  import tools
  
  # Get input to designate system for plotting
  label = input('Enter config file label (e.g. core): ')
  config = tools.load_config(label)
  fig = plt.figure()
  plt.axis('square')
  
  # Define limits of plot relative to the lengths of the rods
  lim = (config['L1'] + config['L2'])*1.25
  
  ax = plt.axes(xlim=(-lim, lim), ylim=(-lim, lim))
  mass1, = ax.plot([], [], 'o', lw=9)
  mass2, = ax.plot([], [], 'o', lw=9)
  rod1, = ax.plot([], [], lw=2)
  rod2, = ax.plot([], [], lw=2)
  
  positions = np.loadtxt('double_positions_%s.txt' % label)
  t = positions[:, 0]
  x1 = positions[:, 1]
  y1 = positions[:, 2]
  x2 = positions[:, 3]
  y2 = positions[:, 4]
  
  
  def init():
      return mass1, mass2, rod1, rod2
  
  
  def animate(i):
      xa, ya, xb, yb = x1[i], y1[i], x2[i], y2[i]
      mass1.set_data([xa], [ya])
      mass2.set_data([xb], [yb])
      rod1.set_data([0.0, xa],  [0.0, ya])
      rod2.set_data([xa, xb],  [ya, yb])
      return mass1, mass2, rod1, rod2
  
  animation = anim.FuncAnimation(fig, animate, init_func=init,
                                 frames=len(t), interval=10, blit=True)
  plt.show()
  
new_contents: # External Packages
  import matplotlib.pyplot as plt
  import matplotlib.animation as anim
  import numpy as np
  
  # Custom Packages
  import tools
  
  # Get input to designate system for plotting
  label = input('Enter config file label (e.g. core): ')
  config = tools.load_config(label)
  fig = plt.figure()
  plt.axis('square')
  
  # Define limits of plot relative to the lengths of the rods
  lim = (config['L1'] + config['L2'])*1.25
  
  ax = plt.axes(xlim=(-lim, lim), ylim=(-lim, lim))
  mass1, = ax.plot([], [], 'o', lw=9)
  mass2, = ax.plot([], [], 'o', lw=9)
  rod1, = ax.plot([], [], lw=2)
  rod2, = ax.plot([], [], lw=2)
  
  positions = np.loadtxt('double_positions_%s.txt' % label)
  t = positions[:, 0]
  x1 = positions[:, 1]
  y1 = positions[:, 2]
  x2 = positions[:, 3]
  y2 = positions[:, 4]
  
  
  def init():
      return mass1, mass2, rod1, rod2
  
  
  def animate(i):
      xa, ya, xb, yb = x1[i], y1[i], x2[i], y2[i]
      mass1.set_data([xa], [ya])
      mass2.set_data([xb], [yb])
      rod1.set_data([0.0, xa],  [0.0, ya])
      rod2.set_data([xa, xb],  [ya, yb])
      return mass1, mass2, rod1, rod2
  
  animation = anim.FuncAnimation(fig, animate, init_func=init,
                                 frames=len(t),
                                 interval=config['interval'],
                                 blit=True)
  plt.show()
  
subject: Update animate.py to handle configu interalr