How to create ID column in R

Question

I have a longitudinal data in a long format. I want to create an ID variable based on the variable-column that identifies each observation of my data. How do I do that in R?

Answer 1

If your name column doesn't just contain single letters (or even if it does), you can use:

dat$id <- as.numeric(as.factor(dat$name))

or, more simply:

dat$id <- c(as.factor(dat$name))

where dat is your data.frame.