library(rpart);

library(rpart.plot)

data(ptitanic);

attr(ptitanic$age,"class") <- NULL;

class(ptitanic$age);

#This is a function which draws the tree

arbre=function(data){

  set.seed(415)

   ptitanicTree  = rpart(survived~., data = data,
                        control = rpart.control(minsplit = 5, cp = 0),
                        method = "class")


   ptitanicOptimal = prune(ptitanicTree,
                           cp = ptitanicTree$cptable[which.min(ptitanicTree$cptable[,4]),1] )


   prp(ptitanicOptimal,extra=1)
}

data1=ptitanic[,c(1,2,3,4,5,6)];

arbre(data1)

# I change the position switching column 5 and 6
data2=ptitanic[,c(1,2,3,4,6,5)];

# Here i get an another tree : why ?
arbre(data2)