将本月的第一个日期转换为R中的datemon

Question

我一直在试图将年份月份作为新列添加到我的以下示例数据集中。

 time site 
1 1/01/2000 A 
2 1/02/2000 A 
3 1/03/2000 A 
4 1/04/2000 A 
5 1/05/2000 A 
6 1/06/2000 A 
7 1/07/2000 A 
8 1/08/2000 A 
9 1/09/2000 A 
10 1/10/2000 A 
11 1/11/2000 A 
12 1/12/2000 A 
13 1/01/2001 A 
14 1/02/2001 A 
15 1/03/2001 A 
16 1/04/2001 A 
17 1/05/2001 A 
18 1/06/2001 A 
19 1/07/2001 A 
20 1/08/2001 A 
21 1/09/2001 A 
22 1/10/2001 A 

可以使用以下dput访问数据集。

dta<-structure(list(time = structure(c(1L, 3L, 5L, 7L, 9L, 11L, 13L, 
15L, 17L, 19L, 21L, 22L, 2L, 4L, 6L, 8L, 10L, 12L, 14L, 16L, 
18L, 20L), .Label = c("1/01/2000", "1/01/2001", "1/02/2000", 
"1/02/2001", "1/03/2000", "1/03/2001", "1/04/2000", "1/04/2001", 
"1/05/2000", "1/05/2001", "1/06/2000", "1/06/2001", "1/07/2000", 
"1/07/2001", "1/08/2000", "1/08/2001", "1/09/2000", "1/09/2001", 
"1/10/2000", "1/10/2001", "1/11/2000", "1/12/2000"), class = "factor"), 
    site = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
    1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "A", class = "factor")), .Names = c("time", 
"site"), class = "data.frame", row.names = c(NA, -22L)) 

我试着用下面的代码，并返回同月所有12

library(zoo) 
dta$y_m = as.yearmon(as.Date(dta$time,"%m/%d/%Y")) 

1] "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2000" 
[8] "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2000" "Jan 2001" "Jan 2001" 
[15] "Jan 2001" "Jan 2001" "Jan 2001" "Jan 2001" "Jan 2001" "Jan 2001" "Jan 2001" 
[22] "Jan 2001" 

任何人可以帮助我，请得到它的权利。谢谢

Answer 1

试试这个：

require(zoo) 
as.yearmon(dta$time, format="%d/%m/%Y") 

输出：

[1] "Jan 2000" "Feb 2000" "Mar 2000" "Apr 2000" "May 2000" "Jun 2000" 
[7] "Jul 2000" "Aug 2000" "Sep 2000" "Oct 2000" "Nov 2000" "Dec 2000" 
[13] "Jan 2001" "Feb 2001" "Mar 2001" "Apr 2001" "May 2001" "Jun 2001" 
[19] "Jul 2001" "Aug 2001" "Sep 2001" "Oct 2001"