Many stacked sessions in one file

# Have: file with observation ids that reset every time the instrument is restarted
# Want: Session identifiers that increment each restart
# Base R approach shown below. Is there a "standard" Tidyverse approach to this?

dat = read.csv(text = "
id,y
RESET
1,1.2
2,3.5
3,2.8
RESET,
1,1.5
2,1.8
3,2.2
4,3.3
RESET,
1,5.4
1,1.1",
stringsAsFactors = FALSE)

starts = which(dat$id == "RESET")
dat$session = cut(
	x = seq_along(dat$id),
	breaks = c(starts, nrow(dat)),
	labels = seq_along(starts),
	right = FALSE,
	include.lowest = TRUE)
dat = dat[-starts,]

dat
#    id   y session
# 2   1 1.2       1
# 3   2 3.5       1
# 4   3 2.8       1
# 6   1 1.5       2
# 7   2 1.8       2
# 8   3 2.2       2
# 9   4 3.3       2
# 11  1 5.4       3
# 12  1 1.1       3

Thanks to @nibrivia for the much cleaner Tidyverse approach: dat %>% mutate(session = cumsum(id=="RESET"), id=as.numeric(id)) %>% drop_na(id)