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

  import numpy as np
  import matplotlib.pyplot as plt
#
#  Boost m = 5, n = 4 to m = 50, n = 40 for better picture.
#
  m = 50
  n = 40
  
  left = 0.0
  right = 3.0
  bottom = 4.0
  top = 8.0
  
  x = np.linspace ( left, right, n )
  y = np.linspace ( top, bottom, m )
  
  X, Y = np.meshgrid ( x, y )
  
  T = X**2 + 3.0 * np.sin ( Y )
#
#  Demonstrate indexing.
#
  i = m // 2
  j = n // 2

  print ( '' )
  print ( '  Array indices [', i, ',', j, '] correspond to' )
  print ( '  X[i,j] = ', X[i,j], '  Y[i,j] = ', Y[i,j], '  T[i,j] = ', T[i,j] )
#
#  Plot the temperature field.
#
  plt.clf ( )
  plt.contour ( X, Y, T )
# plt.contourf ( X, Y, T )
  plt.colorbar ( )
  filename = 'temperature_contour.png'
  plt.savefig ( filename )
  print ( '  Graphics saved as "' + filename + '"' )
  plt.show ( )
  plt.close ( )

  return

if ( __name__ == "__main__" ):
  temperature_contour ( )