在R中按分组将上一行添加到相应列

library(dplyr)

# 创建一个示例数据框
df <- data.frame(
  group = c("A", "A", "B", "B", "C", "C"),
  value = c(1, 2, 3, 4, 5, 6)
)

# 按照group列进行分组，并将上一行的value值添加到新的列prev_value中
df <- df %>%
  group_by(group) %>%
  mutate(prev_value = lag(value))

# 输出结果
df

# A tibble: 6 x 3
# Groups:   group [3]
  group value prev_value
  <chr> <dbl>      <dbl>
1 A         1         NA
2 A         2          1
3 B         3         NA
4 B         4          3
5 C         5         NA
6 C         6          5