# 原数据集
dat1 = data.frame(
x1 = rep(1991:1993, each = 4),
x2 = c(
"a", "b", "c", "e",
"a", "b", "d", "f",
"a", "b", "c", "d"
),
x3 = 1:12
)
dat1
#> x1 x2 x3
#> 1 1991 a 1
#> 2 1991 b 2
#> 3 1991 c 3
#> 4 1991 e 4
#> 5 1992 a 5
#> 6 1992 b 6
#> 7 1992 d 7
#> 8 1992 f 8
#> 9 1993 a 9
#> 10 1993 b 10
#> 11 1993 c 11
#> 12 1993 d 12
# 期望的输出结果
dat2 <- data.frame(
x1 = c(1991, 1991, 1992, 1992, 1993, 1993),
x2 = c("a", "b", "a", "b", "a", "b"),
x3 = c(1, 2, 5, 6, 9, 10)
)
dat2
#> x1 x2 x3
#> 1 1991 a 1
#> 2 1991 b 2
#> 3 1992 a 5
#> 4 1992 b 6
#> 5 1993 a 9
#> 6 1993 b 10
<sup>Created on 2022-09-04 with reprex v2.0.2</sup>
dat2 是 dat1 的子集,按 x1 分组,想筛选在各组都出现的 x2,求助各位。