如何在R中删除多个不同长度的列中的最后一个值(基于组)？

library(dplyr)

# 创建一个示例数据框
df <- data.frame(
  group = c("A", "A", "A", "B", "B", "C", "C", "C"),
  value1 = c(1, 2, 3, 4, 5, 6, 7, 8),
  value2 = c(9, 10, 11, 12, 13, 14, 15, 16),
  value3 = c(17, 18, 19, 20, 21, 22, 23, 24)
)

# 按照group列进行分组，并删除每个组中的最后一个值
df <- df %>%
  group_by(group) %>%
  mutate(
    value1 = ifelse(row_number() == n(), NA, value1),
    value2 = ifelse(row_number() == n(), NA, value2),
    value3 = ifelse(row_number() == n(), NA, value3)
  )

# 查看结果
df