R Error Messages

I spent a good part of yesterday trying to figure what an error message meant. I was trying to draw a classification tree. I kept getting an environmental error message. I couldn’t figure out what was wrong. I searched for answer, only to find nothing useful. Then I remembered about vectorization and turning my data into a data object. I didn’t think I needed it here since I was following the example exactly. But I did.
Useful information on Data objects is in Six Sigma with R, Emilio Cano, Javier Moguerza and Andres Redchuk; Chapter 2.4.

Useful information on subsetting is in R Cookbook, Paul Teetor; Chapter 5.24

examples of what worked.
toycat <-subset(datatoycat, select= c(animal,eye,fur, legs))

toy <- rpart(toycat, method = "class")