Refer to relative rows in R

Question

I know this answer must be out there, but I can\'t figure out how to word the question.

I\'d like to calculate the differences between values in my data.frame.

Answer 1

There are many different ways to do this, but here's one:

f[, "diff"] <- c(NA, diff(f$value))

More generally, if you want to refer to relative rows, you can use lag() or do it directly with indexes:

f[-1,"diff"] <- f[-1, "value"] - f[-nrow(f), "value"]

Answer 2

Use the diff function

f <- cbind(f, c(NA, diff(f[,2])))

Answer 3

If year column isn't sorted then you could use match:

f$diff <- f$value - f$value[match(f$year-1, f$year)]