R语言识别连续3行(1,1,1)数值模式并替换首个匹配项问题

方法1：仅使用dplyr内置函数，无需额外安装依赖 #

library("tidyverse")
# 构造原始数据集
d <- tibble(
  ID = c("a","a","a","a","a","a","a","a"),
  Val = c(8,7,5,4,3,2,1,0),
  outcome = c(1,0,0,1,0,1,1,1)
)

# 生成first_instance变量
d <- d %>% 
  mutate(
    # 逐行判断是否属于连续3个1的序列
    in_triple = outcome == 1 & lead(outcome, default = 0) == 1 & lead(outcome, n = 2, default = 0) == 1 |
                outcome == 1 & lag(outcome, default = 0) == 1 & lead(outcome, default = 0) == 1 |
                outcome == 1 & lag(outcome, default = 0) == 1 & lag(outcome, n = 2, default = 0) == 1,
    first_instance = ifelse(in_triple, 2, 0)
  ) %>% 
  select(-in_triple)

运行后得到的d和你给出的预期结果完全一致。

方法2：使用slider包实现更简洁的滑动窗口判断 #

如果可以安装额外扩展包，用slider的滑动窗口函数逻辑更清晰：

library("tidyverse")
library("slider")

d <- d %>% 
  mutate(
    in_triple = slide_lgl(outcome, ~sum(.x) == 3, .before = 1, .after = 1, .complete = TRUE),
    first_instance = ifelse(in_triple, 2, 0)
  ) %>% 
  select(-in_triple)

内容的提问来源于stack exchange，提问作者Kam