#*****************************************************************************80
#
## grid_fill_contour creates a color contour plot from a table Z(X,Y).
#
#  Discussion:
#
#    The grid is a 41x41 array of values over the region [-2,2]x[-2,2].
#
#  Licensing:
#
#    This code is distributed under the MIT license.
#
#  Modified:
#
#    30 August 2020
#
#  Author:
#
#    John Burkardt
#
cat ( "\n" )
cat ( "grid_fill_contour:\n" )
cat ( " ", version$version.string, "\n" )
cat ( "  Make a filled color contour plot Z(X,Y) for a 41x41 table.\n" )
#
#  Read the data.
#
filename = 'grid_data.txt'
data <- read.table ( file = filename, header = FALSE )
#
#  X and Y are only expected to be vectors, in increasing order.
#  
#  Z is a full matrix.
#
x = data[1:41,1]
y = x
dim = c ( 41, 41 )
z.matrix <- array ( data[,3], dim )

filename = 'grid_fill_contour.png'
png ( filename )

filled.contour ( x, y, z.matrix,
  nlevels = 15,
  main = "Filled contour plot of grid data",
  xlab = "<-- X -->",
  ylab = "<-- Y -->" )

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

quit ( )