Prof. Ripley kindly pointed out to me that the "digits" parameter in
text.tree() is intended to work on numeric labels. The values that I
wanted to modify are not labels (at least not the ones so controlled),
nor are they numeric.
I have since figured out how to do what I want. The values I want to
change are stored within the tree object as character strings. By taking
these strings apart, rounding the numeric component, and putting them
back together I have been able to solve my problem. I have modified my
original code to show what I did:
####################################################
#some fake data
set.seed(123)
f1 <- factor(rep(1:4, 50))
m1 <- matrix(runif(800), nc=4)
d1 <- data.frame(f1, m1)
#the test
library(tree)
mdl1 <- tree(f1 ~ ., data=d1)
#(messy) output
plot(mdl1); text(mdl1, cex=.6)
#minor surgery on the tree object
s1 <- nchar(mdl1$frame$splits[, 1]) > 0
sp1 <- mdl1$frame$splits[s1, 1]
mdl1$frame$splits[s1, 1] <- paste("<", round(as.numeric(substr(sp1,
2, nchar(sp1))), 2), sep="")
#(better) output
plot(mdl1); text(mdl1, cex=.6)
####################################################
Ian Robertson
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