合并R中缺失值和重复测量的两个数据帧

我有两个数据帧,看起来像这样:

df_1 <- tibble(id = c(1,1,1,2,2,2,3,3,3), y = c("a", "b", "c", "a", "b","c", "a", "b", "c"))
df_2 <- tibble(id = c(1,3), z = c(4,6))

我想合并这两个dfs,使其看起来像这样:

df_3 <- tibble(id = c(1,1,1,2,2,2,3,3,3), y = c("a", "b", "c", "a", "b","c", "a", "b", "c"), z = c(4,4,4,NA,NA,NA,6,6,6))

在R你将如何做到这一点?非常感谢。