Adding a ranking column to a dataframe

Question

This seems like it must be a very common task, but I can't find a solution in google or SO. I want to add a column called 'rank' to 'dat1' based on the sequence that 'order.scores' applies to 'dat'. I tried using row.names(), but the rownames are based on 'dat', not 'dat1'. I also tried 'dat$rank <-rank(dat1)', but this produces an error message.

fname<-c("Joe", "Bob", "Bill", "Tom", "Sue","Sam","Jane","Ruby")
score<-c(500, 490, 500, 750, 550, 500, 210, 320)
dat<-data.frame(fname,score)
order.scores<-order(dat$score,dat$fname)
dat1<-dat[order.scores,]

Answer 1

You can compute a ranking from an ordering as follows:

dat$rank <- NA
dat$rank[order.scores] <- 1:nrow(dat)
dat
#   fname score rank
# 1   Joe   500    5
# 2   Bob   490    3
# 3  Bill   500    4
# 4   Tom   750    8
# 5   Sue   550    7
# 6   Sam   500    6
# 7  Jane   210    1
# 8  Ruby   320    2