function diffusivity_2d_bnt_contour ( )

%*****************************************************************************80
%
%% diffusivity_2d_bnt_contour() displays contour plots of a 2D stochastic diffusivity function.
%
%  Discussion:
%
%    The diffusivity function is computed by DIFFUSIVITY_2D_BNT.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    08 February 2019
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Ivo Babuska, Fabio Nobile, Raul Tempone,
%    A stochastic collocation method for elliptic partial differential equations
%    with random input data,
%    SIAM Journal on Numerical Analysis,
%    Volume 45, Number 3, 2007, pages 1005-1034.
%
  fprintf ( 1, '\n' );
  fprintf ( 1, 'diffusivity_2d_bnt_contour\n' );
  fprintf ( 1, '  Display contour or surface plots of the stochastic\n' );
  fprintf ( 1, '  diffusivity function defined by DIFFUSIVITY_2D_BNT.\n' );
%
%  Set the spatial grid.
%
  nx = 151;
  ny = 121;

  x_1d = linspace ( -1.5, 0.0, nx );
  y_1d = linspace ( -0.4, 0.8, ny );

  [ X, Y ] = meshgrid ( x_1d, y_1d );
%
%  Sample OMEGA.
%
  m = 4;
  omega = rand ( m, 1 );
%
%  Compute the diffusivity field, using a uniform OMEGA.
%
  dc0 = 10.0;
  n = nx * ny;
  DC = diffusivity_2d_bnt ( dc0, omega, n, X, Y );
%
%  Plot the diffusivity field as a surface plot.
%
  figure ( )
  surf ( Y, X, DC, 'EdgeColor', 'interp' )
  xlabel ( '<--- Y --->', 'fontsize', 12 )
  ylabel ( '<--- X --->', 'fontsize', 12 )
  zlabel ( '<--- \rho(X,Y) --->', 'fontsize', 12 )
  title ( 'BNT stochastic diffusivity function', 'Fontsize', 18 )

  filename = 'diffusivity_2d_bnt.png';
  print ( '-dpng', filename )
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Plot file stored as "%s".\n', filename );

  pause ( 5 );

  close ( );

  return
end
