我有这个df:
> fechas <- c("1991-01-01", "1991-01-03", "1991-01-04", "1991-01-05",
+ "1991-01-08", "1991-01-09", "1991-01-11", "1991-01-13", "1991-01-15",
+ "1991-01-16", "1991-01-20", "1991-01-21", "1991-01-27", "1991-01-29",
+ "1991-02-06", "1991-02-07", "1991-02-08", "1991-02-09", "1991-02-10",
+ "1991-02-11", "1991-02-12", "1991-02-16")
> index <- c(1:10)
> df <- merge (index,fechas)
我首先使用 lubridate 将“y”因子变量转换为 POSIXct,如下所示:
library (lubridate)
df$fecha <- ymd (df$y)
220 parsed with %Y-%m-%d
str(df)
'data.frame': 220 obs. of 3 variables:
$ x : int 1 2 3 4 5 6 7 8 9 10 ...
$ y : Factor w/ 22 levels "1991-01-01","1991-01-03",..: 1 1 1 1 1 1 1 1 1 1 ...
$ fecha: POSIXct, format: "1991-01-01" "1991-01-01" "1991-01-01" "1991-01-01" ...
然后我为计算生成参考数据并继续
> start_1991 <- ymd("1991-01-01")
1 parsed with %Y-%m-%d
> df$jul <- (df$fecha-start_1991)+1
我得到了一个奇怪的结果,朱利安天数很高
fecha2 jul
1991-01-03 172801
1991-01-04 259201
1991-01-05 345601
1991-01-08 604801
有些年份运行良好,这是我在不同数据帧中使用的常见程序
任何的想法?
谢谢!!