Reading rpart Input Parameters from a Text Variable

Question

I\'m using rpart to make a decision tree. For example:

fit <- rpart(Kyphosis ~ Age + Number + Start, data=kyphosis)

How do

Answer 1

Try simply passing the formula as a character string:

rpart_formula <-paste("Kyphosis ~ ",paste(predictor_variables, collapse="+"))

that should be coerced to a formula by rpart.

Edit

As noted in the comments below, not all functions will do the coercion for you, so you should not rely on this behavior, but in this case rpart most certainly does.

Answer 2

Use as.formula:

rpart_formula <- as.formula(
    paste("Kyphosis ~ ", 
          paste(predictor_variables, collapse = " + "), 
          sep = ""
    )
)