Percentile for Each Observation w/r/t Grouping Variable

Question

I have some data that looks like the following. It is grouped by variable \"Year\" and I want to extract the percentiles of each observation of Score, with respect to t

Answer 1

Using data.table is pretty straight-forward as well. Just for completeness and also as an easy way to find the data.table solution.

library(data.table)
year <- rep(2001:2005, 2)
score <- round(rnorm(10, 35, 3))

dt <- data.table(score)


dt[, .(Percentile = ecdf(score)(score)), by = list(year)]