如何获取列的最大值，当该列中的某个值在R中满足时重置最大值

Question

Specifically, I have a data look like this:

counter
1
2
3
1
1
2
3
4
5
6          

and I am looking for a new_column that can get the max value rowwise until it hit 1, which reset the whole process.

counter | new_column
1       |  3
2       |  3
3       |  3
1       |  1
1       |  6
2       |  6
3       |  6
4       |  6
5       |  6
6       |  6

How to achieve that in R/dplyr ?

Answer 1

Here's a straightforward solution:

library(dplyr)
df %>%
  group_by(group = cumsum(counter == 1)) %>%
  mutate(max = max(counter)) %>%
  ungroup() %>%
  select(-group)
# # A tibble: 10 × 2
#   counter   max
#     <dbl> <dbl>
# 1       1     3
# 2       2     3
# 3       3     3
# 4       1     1
# 5       1     6
# 6       2     6
# 7       3     6
# 8       4     6
# 9       5     6
#10       6     6