I encountered the question: "Cumulative sum that resets when 0 is encountered" via https://stackoverflow.com/a/32502162/13269143 , which partially, but not fully, answered my question. I first wanted to create a column that, row-wise, accumulates the values of each sequence in column b that is separated by a 0. This I achieved by using the code:
setDT(df)[, whatiwant := cumsum(b), by = rleid(b == 0L)]
as suggested in https://stackoverflow.com/a/32502162/13269143 (the other solutions provided did not work for me. They only produced NA values.) Now, I wish to also create a third column, "What I Want" in the illustration, that assigns the maximum aggregated value of the accumulated value for a given sequence to each observation in that particular sequence. Let me illustrate,
b Accumulated What I Want
1 1 3
1 2 3
1 3 3
0 0 0
1 1 4
1 2 4
1 3 4
1 4 4
0 0 0
0 0 0
0 0 0
1 1 2
1 2 2
There might be a very simple way to do this. Thank you in advance.
You can use max instead of cumsum in your attempt :
library(data.table)
setDT(df)[, whatiwant := max(Accumulated), by = rleid(b == 0L)]
df
# b Accumulated whatiwant
# 1: 1 1 3
# 2: 1 2 3
# 3: 1 3 3
# 4: 0 0 0
# 5: 1 1 4
# 6: 1 2 4
# 7: 1 3 4
# 8: 1 4 4
# 9: 0 0 0
#10: 0 0 0
#11: 0 0 0
#12: 1 1 2
#13: 1 2 2