title: Bessel function using scipy.quad integration not working
body: <p>I'm trying to plot a Bessel function in 2D using the scipy.quad integration method. </p>
  
  <p>My problem: the plot only has a tiny dot in the middle because my lowest value is far too low.</p>
  
  <p>Here is my code:</p>
  
  <pre class="lang-py prettyprint-override"><code>import numpy as np
  import scipy.integrate as si
  import matplotlib.pyplot as plt
  
  wavelength = 5.0
  k = 2 * np.pi / wavelength
  
  side = 100.0
  points = 100
  spacing = side / points
  
  
  def J(x, m):
      def f(t):
          return np.cos(m * t - x * np.sin(t)) / np.pi
  
      y = si.quad(f, 0, np.pi)
      return y[0]
  
  
  x1 = side / 2
  y1 = side / 2
  
  
  data = np.empty([points, points], float)
  data[0, 0] = 0.5
  
  for i in range(1, points):
      y = spacing * i
      for j in range(1, points):
          x = spacing * j
          r = np.sqrt((x - x1) ** 2 + (y - y1) ** 2)
          if r == 0:
              data[i, j] = 1
          else:
              data[i, j] = (2 * J(1, r) / r) ** 2
  print(data.min(), data.max())
  plt.imshow(data, origin="lower", extent=[0, side, 0, side])
  plt.show()
  </code></pre>