#*****************************************************************************80
#
## iris_decision_tree plots a decision tree for Iris classification.
#
#  Licensing:
#
#    This code is distributed under the MIT license. 
#
#  Modified:
#
#    04 September 2020
#
#  Author:
#
#    John Burkardt
#
cat ( date ( ), "\n" )
cat ( "\n" )
cat ( "iris_decision_tree\n" )
cat ( " ", version$version.string, "\n" )
cat ( "  Plot a decision tree for the iris classification task." )

library ( igraph )

filename = "iris_decision_tree.png"
png ( filename )

G <- graph.tree ( n = 1, children = 2 )
V(G)$name <- "Start"

G <- G + vertices ( "setosa" )
G <- G + edge ( "Start", "setosa", label = "x3 < 2.45" )
G <- G + vertices ( "1" )
G <- G + edge ( "Start", "1", label = "2.45 <= x3" )

G <- G + vertices ( "2" )
G <- G + edge ( "1", "2", label = "x4 < 1.75" )
G <- G + vertices ( "virginica(1)" )
G <- G + edge ( "1", "virginica(1)", label = "1.75 <= x4" )

G <- G + vertices ( "3" )
G <- G + edge ( "2", "3", label = "x3 < 4.95" )
G <- G + vertices ( "virginica(2)" )
G <- G + edge ( "2", "virginica(2)", label = "4.95 <= x3" )

G <- G + vertices ( "versicolor" )
G <- G + edge ( "3", "versicolor", label = "x4 < 1.65" )
G <- G + vertices ( "virginica(3)" )
G <- G + edge ( "3", "virginica(3)", label = "1.65 <= x4" )

my_layout <- layout.reingold.tilford ( G, params = list ( root = "Start" ) )
plot ( G, layout = my_layout, vertex.size = 40, 
  main = "Iris_decision_tree" )

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

quit ( )