基于条件修改特定变量的值

使用data.table:

setDT(data)

data[, rating := ifelse(cumsum(rating == "F") >= 1, "F", rating), by = ID]

data
    ID PERIOD rating
 1:  8      0      3
 2:  8      1      3
 3:  8      2      2
 4:  8      3      F
 5:  8      4      F
 6:  8      5      F
 7:  8      6      F
 8:  9      0      2
 9:  9      1      2
10:  9      2      1

在哪里?

data <- data.frame(
  ID = c(8L, 8L, 8L, 8L, 8L, 8L, 8L, 9L, 9L, 9L), 
  PERIOD = c(0L, 1L, 2L, 3L, 4L, 5L, 6L, 0L, 1L, 2L), 
  rating = c("3", "3", "2", "F", "3", "F", "1", "2", "2", "1"),
  stringsAsFactors = FALSE
)

编辑

data[, rating := ifelse(cumsum(rating == "F"), "F", rating), by = ID]

编辑2

正如Ronak建议的那样,您可以使用base R附带的ave()执行如下操作:

data$rating <- 
  ifelse(ave(data$rating == "F", data$ID, FUN = cumsum), "F", data$rating) 

library(dplyr)
data %>% 
     group_by(ID) %>% 
     mutate(rating  = replace(rating, row_number() > which(rating == "F")[1], "F" ))
# A tibble: 10 x 3
# Groups:   ID [2]
#      ID PERIOD rating
#   <int>  <int> <chr> 
# 1     8      0 3     
# 2     8      1 3     
# 3     8      2 2     
# 4     8      3 F     
# 5     8      4 F     
# 6     8      5 F     
# 7     8      6 F     
# 8     9      0 2     
# 9     9      1 2     
#10     9      2 1