coding variable values into classes using R

Question

I have a set of data in which I need to code values of certain variables (numeric) into 3 classes.

My data set is similar to this but has 60 more variables:

Answer 1

I think Greg's answers cover "standard operating procedure", but I find many uses for the findInterval function as well. It naturally returns a number that identifies the interval in the second argument.

 data$int <- findInterval(data$wt, c(179, 200, 300, Inf))
 data