text: """
  Compute the Mandelbrot fractal
  """
  import numpy as np
  import matplotlib.pyplot as plt
  from numpy import newaxis
  
  def compute_mandelbrot(N_max, some_threshold, nx, ny):
      # A grid of c-values
      x = np.linspace(-2, 1, nx)
      y = np.linspace(-1.5, 1.5, ny)
  
      c = x[:,newaxis] + 1j*y[newaxis,:]
  
      # Mandelbrot iteration
  
      z = c
      for j in xrange(N_max):
          z = z**2 + c
  
      mandelbrot_set = (abs(z) < some_threshold)
  
      return mandelbrot_set
  
  # Save
  
  mandelbrot_set = compute_mandelbrot(50, 50., 601, 401)
  
  plt.imshow(mandelbrot_set.T, extent=[-2, 1, -1.5, 1.5])
  plt.gray()
  plt.savefig('mandelbrot.png')
  