- llibrary(dplyr)
- library(zoo)
- out <- data %>%
- group_by(id) %>%
- mutate(session = 1:length(jiemu), session0 = session) %>%
- mutate(session = ifelse(time <=20 & session0 != 1, NA, session)) %>%
- mutate(session = na.locf(session, na.rm = F)) %>%
- select(-session0)