#*****************************************************************************80
#
## tsp_dantzig42_graph() plots a traveling salesman tour.
#
#  Discussion:
#
#    This code uses the Rgraphviz package.
#
#  Licensing:
#
#    This code is distributed under the MIT license. 
#
#  Modified:
#
#    26 July 2026
#
#  Author:
#
#    John Burkardt
#
cat ( "\n" )
cat ( "tsp_dantzig42_graph():\n" )
cat ( " ", version$version.string, "\n" )
cat ( "  Plot a traveling salesman route as a graph.\n" )

source ( "/home/john/public_html/r_src/tsp_dantzig42/tsp_dantzig42_order.R" )  
source ( "/home/john/public_html/r_src/tsp_dantzig42/tsp_dantzig42_xy.R" )

n <- 42
order <- tsp_dantzig42_order ( )
xy <- tsp_dantzig42_xy ( )
#
#  Make a copy of the data in the optimal order.
#
xy2 <- xy

for ( i in 1 : n )
{
  xy2[i,1] = xy[order[i],1]
  xy2[i,2] = xy[order[i],2]
}
#
#  Repeat first city at end, to close the loop.
#
xy2 = rbind ( xy2, xy2[1,1:2] )
#
#  Plot the data.
#
filename = "tsp_dantzig42_graph.png"

png ( filename )

plot ( xy2[,1], xy2[,2],
  xlab = "<--- X --->",
  ylab = "<--- Y --->",
  main = "TSP Dantzig42",
  col = "blue",
  type = 'l' )

grid ( nx = 5, ny = 5, col = "black" )

cat ( '  Graphics saved as "', filename, '"\n' )
#
#  Terminate.
#
cat ( "\n" )
cat ( "tsp_dantzig42_graph():\n" )
cat ( "  Normal end of execution.\n" )
quit ( )