我想将日期转换为朱利安日
x <- c('5/5/2007')
# convert to day of year (Julian date)
strptime(x, "%m/%d/%Y")$yday+1
#125
我有两件事我不明白：
1）y$day + 1在做什么？
当我运行更多日期时，它会在某些日期给我NA。
date<-c("09/06/1997","01/06/1998","26/05/1999","02/06/2000","01/06/2001","06/06/2002","05/06/2003",
"21/05/2004","16/06/2005","27/05/2006","08/06/2007","09/06/1997","01/06/1998")
strptime(date, "%m/%d/%Y")$yday+1
[1] 249 6 NA 37 6 157 126 NA NA NA 218 249 6
我不确定为什么会这样？为什么我们需要$yday+1