Grouping of R dataframe by connected values

Question

I didn\'t find a solution for this common grouping problem in R:

This is my original dataset

ID  State
1   A
2   A
3   B
4   B
5   B
6   A
7   A
8            


        

Answer 1

Here is another attempt using rle and aggregate from base R:

rl <- rle(df$State)
newdf <- data.frame(ID=df$ID, State=rep(1:length(rl$lengths),rl$lengths))
newdf <- aggregate(ID~State, newdf, FUN = function(x) c(minID=min(x), maxID=max(x)))
newdf$State <- rl$values

  # State ID.minID ID.maxID
# 1     A        1        2
# 2     B        3        5
# 3     A        6        8
# 4     C        9       10

data

df <- structure(list(ID = 1:10, State = c("A", "A", "B", "B", "B", 
"A", "A", "A", "C", "C")), .Names = c("ID", "State"), class = "data.frame", 
row.names = c(NA, 
    -10L))