#! /usr/bin/env python3
#
def sombrero_surface ( ):

#*****************************************************************************80
#
## sombrero_surface() draws a surface plot of sombrero data.
#
#  Licensing:
#
#    This code is distributed under the GNU LGPL license.
#
#  Modified:
#
#    19 April 2019
#
#  Author:
#
#    John Burkardt
#
  import matplotlib.pyplot as plt
  import numpy as np
  from mpl_toolkits.mplot3d import Axes3D
  from matplotlib import cm

  print ( '' )
  print ( 'sombrero_surface():' )
  print ( '  Make a surface plot Z(X,Y) of the sombrero function.' )
#
#  Set up X, Y grid and Z data.
#
  xvec = np.linspace( -8.0, 8.0, 33 )
  yvec = np.linspace( -8.0, 8.0, 33 )
  xmat, ymat = np.meshgrid ( xvec, yvec )
  rmat = np.sqrt ( xmat**2 + ymat**2 )
  zmat = np.sin ( rmat ) / rmat 
  zmat[ rmat == 0 ] = 1.0
#
#  Form the figure.
#
  fig = plt.figure ( )
  ax = fig.add_subplot ( 111, projection='3d' )
  surface = ax.plot_surface ( xmat, ymat, zmat, \
    cmap = cm.twilight, edgecolor = 'none' )
  fig.colorbar ( surface )
  ax.set_title ( 'The sombrero function', fontsize = 16 )
  ax.set_xlabel ( '<--- X --->', fontsize = 16 )
  ax.set_ylabel ( '<--- Y --->', fontsize = 16 )
  ax.set_zlabel ( '<--- Z(X,Y) --->', fontsize = 16 )
  filename = 'sombrero_surface.png'
  plt.savefig ( filename )
  print ( '  Graphics saved as "%s"' % ( filename ) )
  plt.show ( )
  plt.close ( )

  return

if ( __name__ == '__main__' ):
  sombrero_surface ( )