How to drop unused levels after filtering by factor? [duplicate]

Answer 1

You could do something like:

dat1 <- dat0 %>%
  filter(s == "spring") %>% 
  droplevels()

Then

str(df)
#'data.frame':  1 obs. of  3 variables:
# $ f: Factor w/ 1 level "a": 1
# $ s: Factor w/ 1 level "spring": 1
# $ v: num 5

Answer 2

You could use droplevels

 sp.tmp <- droplevels(sp.tmp)
 str(sp.tmp)
 #'data.frame': 1 obs. of  3 variables:
 #$ f: Factor w/ 1 level "a": 1
 #$ s: Factor w/ 1 level "spring": 1
# $ v: num 5