[R] Error when I try to build / plot a tree using rpart()

[Jude Ryan]

Hi,

I am using the rpart package to build a classification tree. I did 
manage to build a tree with data on a previous project. However, when 
attampting to build a tree on a project I am working on, I seem to be 
getting the error shown below:

 > nhg3.rp <- rpart(profitresp ~., nhg3, method="class")
 > plot(nhg3.rp, branch=0.4, uniform=T); text(nhg3.rp, digits=3)
Error in yval[, 1] : incorrect number of dimensions

The distribution of my binary dependent variable is:
 > table(nhg$profitresp)

   0    1
3703 4360

I am using 105 potential predictor variables. I am trying to come up 
with a decision rule to identify profitable responders from 
non-responders to a mailing.

Some other details are:
 > summary(nhg3.rp)
Call:
rpart(formula = profitresp ~ ., data = nhg3, method = "class")
  n= 8063

           CP nsplit rel error
1 0.009451796      0         1
Error in yval[, 1] : incorrect number of dimensions

 > print(nhg3.rp)
n= 8063

node), split, n, loss, yval, (yprob)
      * denotes terminal node

1) root 8063 3703 1 (0.4592583 0.5407417) *

 > printcp(nhg3.rp)

Classification tree:
rpart(formula = profitresp ~ ., data = nhg3, method = "class")

Variables actually used in tree construction:
character(0)

Root node error: 3703/8063 = 0.45926

n= 8063

         CP nsplit rel error
1 0.0094518      0         1

Any help is appreciated.

Thanks much,

Jude Ryan