Reputation: 273
Here is the code to rank based on column v2:
x <- data.frame(v1 = c(2,1,1,2), v2 = c(1,1,3,2))
x$rank1 <- rank(x$v2, ties.method='first')
But I really want to rank based on both v2 and/then v1 since there are ties in v2. How can I do that without using RPostgreSQL?
Upvotes: 8
Views: 10397
Reputation: 3066
Try this:
x <- data.frame(v1 = c(2,1,1,2), v2 = c(1,1,3,2))
# The order function returns the index (address) of the desired order
# of the examined object rows
orderlist<- order(x$v2, x$v1)
# So to get the position of each row in the index, you can do a grep
x$rank<-sapply(1:nrow(x), function(x) grep(paste0("^",x,"$"), orderlist ) )
x
# For a little bit more general case
# With one tie
x <- data.frame(v1 = c(2,1,1,2,2), v2 = c(1,1,3,2,2))
x$rankv2<-rank(x$v2)
x$rankv1<-rank(x$v1)
orderlist<- order(x$rankv2, x$rankv1)
orderlist
#This rank would not be appropriate
x$rank<-sapply(1:nrow(x), function(x) grep(paste0("^",x,"$"), orderlist ) )
#there are ties
grep(T,duplicated(x$rankv2,x$rankv1) )
# Example for only one tie
makeTieRank<-mean(x[which(x[,"rankv2"] %in% x[grep(T,duplicated(x$rankv2,x$rankv1) ),][,c("rankv2")] &
x[,"rankv1"] %in% x[grep(T,duplicated(x$rankv2,x$rankv1) ),][,c("rankv1")]),]$rank)
x[which(x[,"rankv2"] %in% x[grep(T,duplicated(x$rankv2,x$rankv1) ),][,c("rankv2")] &
x[,"rankv1"] %in% x[grep(T,duplicated(x$rankv2,x$rankv1) ),][,c("rankv1")]),]$rank<-makeTieRank
x
Upvotes: 0
Reputation: 25838
Here we create a sequence of numbers and then reorder it as if it was created near the ordered data:
x$rank <- seq.int(nrow(x))[match(rownames(x),rownames(x[order(x$v2,x$v1),]))]
Or:
x$rank <- (1:nrow(x))[order(order(x$v2,x$v1))]
Or even:
x$rank <- rank(order(order(x$v2,x$v1)))
Upvotes: 0
Reputation: 1580
order
works, but for manipulating data frames, also check out the plyr
and dplyr
packages.
> arranged_x <- arrange(x, v2, v1)
Upvotes: 3
Reputation: 44634
How about:
within(x, rank2 <- rank(order(v2, v1), ties.method='first'))
# v1 v2 rank1 rank2
# 1 2 1 1 2
# 2 1 1 2 1
# 3 1 3 4 4
# 4 2 2 3 3
Upvotes: 3