R version 2.7.0 (2008-04-22)
Copyright (C) 2008 The R Foundation for Statistical Computing
ISBN 3-900051-07-0

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> library(rpart);
> 
> train <- read.table("loans.dat",header=F,col.names=c("x1","x2","y"));
> n <- length(train$y)
> 
> size <- 100;
> 
> grid <- mat.or.vec((size+1)*(size+1),2);
> for (i in 0:size) {
+ for (j in 0:size) {
+   ij <- (size+1)*j+i+1
+   grid[ij,1] <- i;
+   grid[ij,2] <- j;
+ }
+ }
> grid <- grid/(size+1);
> 
> gx1 <- grid[,1];
> gx2 <- grid[,2];
> 
> dflt <- (gx1 < 0.3440913);
> 
> errors <- 0
> for (i in 1:n) {
+   errors <- errors + abs(train$y[i] - (train$x1[i] < 0.3440913))
+ }
> print(paste("Errors = ", errors))
[1] "Errors =  21"
> 
> edge <- mat.or.vec((size+1)*(size+1),1);
> edge <- as.logical(edge);
> for (i in 1:size) {
+ for (j in 1:size) {
+   left <- (size+1)*j+i+1;
+   rite <- (size+1)*(j-1)+i+1;
+   top  <- left;
+   bot  <- left - 1;
+   edge[left] <- 
+     ( dflt[left] && !dflt[rite] ) ||
+     ( !dflt[left] && dflt[rite] ) ||
+     ( dflt[top]  && !dflt[bot]  ) || 
+     ( !dflt[top]  && dflt[bot]  ) ;
+ }
+ }
> 
> X <- cbind(train$x1,train$x2);
> y <- (train$y==1);
> 
> if (!exists("ps.default")) ps.default <- ps.options()
> ps.options(horizontal=FALSE,onefile=FALSE);
> ps.options(paper="special",pagecentre=FALSE);
> ps.options(width=8.0,height=4.0);
> 
> postscript(file="treelec01.eps");
> par(mfrow=c(1,2),mar=c(4,4,1.5,2)+0.1) # mar=c(bottom,left,top,right)
> 
> plot(X,type='n',xlab="FICO Score",ylab="P-Index");
> points(X[y,],pch='o',col="red");
> points(X[!y,],pch='o',col="green");
> points(grid[dflt,],pch='.',col="red");
> points(grid[!dflt,],pch='.',col="green");
> points(grid[edge,],pch='+',col="black",cex=0.4);
> 
> grid <- mat.or.vec((size+1)*(size+1),2);
> for (i in 0:size) {
+ for (j in 0:size) {
+   ij <- (size+1)*j+i+1
+   grid[ij,1] <- i;
+   grid[ij,2] <- j;
+ }
+ }
> grid <- grid/(size+1);
> 
> gx1 <- grid[,1];
> gx2 <- grid[,2];
> 
> dflt <- (gx2 < 0.3520624);
> 
> errors <- 0
> for (i in 1:n) {
+   errors <- errors + abs(train$y[i] - (train$x2[i] < 0.3520624))
+ }
> print(paste("Errors = ", errors))
[1] "Errors =  47"
> 
> edge <- mat.or.vec((size+1)*(size+1),1);
> edge <- as.logical(edge);
> for (i in 1:size) {
+ for (j in 1:size) {
+   left <- (size+1)*j+i+1;
+   rite <- (size+1)*(j-1)+i+1;
+   top  <- left;
+   bot  <- left - 1;
+   edge[left] <- 
+     ( dflt[left] && !dflt[rite] ) ||
+     ( !dflt[left] && dflt[rite] ) ||
+     ( dflt[top]  && !dflt[bot]  ) || 
+     ( !dflt[top]  && dflt[bot]  ) ;
+ }
+ }
> 
> X <- cbind(train$x1,train$x2);
> y <- (train$y==1);
> 
> plot(X,type='n',xlab="FICO Score",ylab="P-Index");
> points(X[y,],pch='o',col="red");
> points(X[!y,],pch='o',col="green");
> points(grid[dflt,],pch='.',col="red");
> points(grid[!dflt,],pch='.',col="green");
> points(grid[edge,],pch='+',col="black",cex=0.4);
> 
> dev.off();
null device 
          1 
> 
> grid <- mat.or.vec((size+1)*(size+1),2);
> for (i in 0:size) {
+ for (j in 0:size) {
+   ij <- (size+1)*j+i+1
+   grid[ij,1] <- i;
+   grid[ij,2] <- j;
+ }
+ }
> grid <- grid/(size+1);
> 
> gx1 <- grid[,1];
> gx2 <- grid[,2];
> 
> dflt <- (gx1 < 0.3440913) | ( (gx1 >= 0.3440913) & (gx2 < 0.2215745) );
> dflt0 <- (gx1 < 0.3440913)
> 
> errors <- 0
> for (i in 1:n) {
+   x1 <- train$x1[i]
+   x2 <- train$x2[i]
+   y  <- train$y[i]
+   yhat <- (x1 < 0.3440913) | ( (x1 >= 0.3440913) & (x2 < 0.2215745) );
+   errors <- errors + abs(y - yhat)
+ }
> print(paste("Errors = ", errors))
[1] "Errors =  15"
> 
> edge <- mat.or.vec((size+1)*(size+1),1);
> edge <- as.logical(edge);
> for (i in 1:size) {
+ for (j in 1:size) {
+   left <- (size+1)*j+i+1;
+   rite <- (size+1)*(j-1)+i+1;
+   top  <- left;
+   bot  <- left - 1;
+   edge[left] <- 
+     ( dflt[left] && !dflt[rite] ) ||
+     ( !dflt[left] && dflt[rite] ) ||
+     ( dflt[top]  && !dflt[bot]  ) || 
+     ( !dflt[top]  && dflt[bot]  ) ||
+     ( dflt0[left] && !dflt0[rite] ) ||
+     ( !dflt0[left] && dflt0[rite] ) ||
+     ( dflt0[top]  && !dflt0[bot]  ) || 
+     ( !dflt0[top]  && dflt0[bot]  )
+ }
+ }
> 
> X <- cbind(train$x1,train$x2);
> y <- (train$y==1);
> 
> postscript(file="treelec02.eps");
> par(mfrow=c(1,2),mar=c(4,4,1.5,2)+0.1) # mar=c(bottom,left,top,right)
> 
> plot(X,type='n',xlab="FICO Score",ylab="P-Index");
> points(X[y,],pch='o',col="red");
> points(X[!y,],pch='o',col="green");
> points(grid[dflt,],pch='.',col="red");
> points(grid[!dflt,],pch='.',col="green");
> points(grid[edge,],pch='+',col="black",cex=0.4);
> 
> grid <- mat.or.vec((size+1)*(size+1),2);
> for (i in 0:size) {
+ for (j in 0:size) {
+   ij <- (size+1)*j+i+1
+   grid[ij,1] <- i;
+   grid[ij,2] <- j;
+ }
+ }
> grid <- grid/(size+1);
> 
> gx1 <- grid[,1];
> gx2 <- grid[,2];
> 
> dflt <- (gx1 < 0.3440913) & (gx2 < 0.75) 
> dflt0 <- (gx1 < 0.3440913)
> 
> errors <- 0
> for (i in 1:n) {
+   x1 <- train$x1[i]
+   x2 <- train$x2[i]
+   y  <- train$y[i]
+   yhat <- (x1 < 0.3440913) & (x2 < 0.75)
+   errors <- errors + abs(y - yhat)
+ }
> print(paste("Errors = ", errors))
[1] "Errors =  21"
> 
> edge <- mat.or.vec((size+1)*(size+1),1);
> edge <- as.logical(edge);
> for (i in 1:size) {
+ for (j in 1:size) {
+   left <- (size+1)*j+i+1;
+   rite <- (size+1)*(j-1)+i+1;
+   top  <- left;
+   bot  <- left - 1;
+   edge[left] <- 
+     ( dflt[left] && !dflt[rite] ) ||
+     ( !dflt[left] && dflt[rite] ) ||
+     ( dflt[top]  && !dflt[bot]  ) || 
+     ( !dflt[top]  && dflt[bot]  ) ||
+     ( dflt0[left] && !dflt0[rite] ) ||
+     ( !dflt0[left] && dflt0[rite] ) ||
+     ( dflt0[top]  && !dflt0[bot]  ) || 
+     ( !dflt0[top]  && dflt0[bot]  )
+ }
+ }
> 
> X <- cbind(train$x1,train$x2);
> y <- (train$y==1);
> 
> plot(X,type='n',xlab="FICO Score",ylab="P-Index");
> points(X[y,],pch='o',col="red");
> points(X[!y,],pch='o',col="green");
> points(grid[dflt,],pch='.',col="red");
> points(grid[!dflt,],pch='.',col="green");
> points(grid[edge,],pch='+',col="black",cex=0.4);
> 
> dev.off()
null device 
          1 
> 
> proc.time()
   user  system elapsed 
  2.614   0.048   2.660