I have a data frame like so:
我有一个这样的数据框架:
df <- structure(list(year = c(1990, 1990, 1990, 1990, 1990, 1990, 1990,
1990, 1990, 1990, 1990, 1990, 1990, 1990, 1990, 1991, 1991, 1991,
1991, 1991, 1991, 1991, 1991, 1991, 1991, 1991, 1991, 1991, 1991,
1991), group = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
2L, 2L, 2L, 2L, 2L), .Label = c("A", "B"), class = "factor"),
value = c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L,
13L, 14L, 15L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L,
15L, 16L, 17L, 18L, 19L)), .Names = c("year", "group", "value"
), row.names = c(NA, -30L), class = "data.frame")
> df
year group value
1 1990 A 1
2 1990 A 2
3 1990 A 3
4 1990 A 4
5 1990 A 5
6 1990 A 6
7 1990 B 7
8 1990 B 8
9 1990 B 9
10 1990 B 10
11 1990 B 11
12 1990 B 12
13 1990 B 13
14 1990 B 14
15 1990 B 15
16 1991 A 5
17 1991 A 6
18 1991 A 7
19 1991 A 8
20 1991 A 9
21 1991 A 10
22 1991 A 11
23 1991 A 12
24 1991 A 13
25 1991 A 14
26 1991 B 15
27 1991 B 16
28 1991 B 17
29 1991 B 18
30 1991 B 19
d
