#*****************************************************************************80
#
## mexican_hat_surface makes a 3D surface plot of "Mexican hat" data.
#
#  Licensing:
#
#    This code is distributed under the MIT license.
#
#  Modified:
#
#    30 August 2020
#
#  Author:
#
#    John Burkardt
#
mexican_hat <- function ( x, y )
{
  r <- sqrt ( x^2 + y^2 + 0.000001 )
  z = sin ( r ) / r
}

cat ( "\n" )
cat ( "mexican_hat_surface:\n" )
cat ( " ", version$version.string, "\n" )
cat ( "  Make a 3D surface plot of Mexican hat data.\n" )
#
#  Create the data
#
x = seq ( from = -8.0, to = +8.0, len = 33 )
y = seq ( from = -8.0, to = +8.0, len = 33 )
z = outer ( x, y, mexican_hat )

filename = 'mexican_hat_surface.png'
png ( filename )

persp ( x, y, z,
  theta = 60,
  phi = 30,
  main = "Mexican Hat function",
  col = "orange" )

cat ( "\n" )
cat ( "  Graphics saved as '", filename, "'\n" )
#
#  Terminate.
#
cat ( "\n" )
cat ( "mexican_hat_surface:\n" )
cat ( "  Normal end of execution.\n" )

quit ( )