[R] calculating the number of days from dates

[Knut Krueger]

Bob Green schrieb:
>
>  > dates <- read.csv("c:\\dates.csv",header=T)
>  > dates
>            v1         v2
> 1 12/12/1978 12/12/2005
> 2 23/01/1965 23/09/2001
> 3 24/12/2004 16/03/2007
> 4  3/03/2003  4/04/2004
> 5  8/11/2006  1/05/2007
>
>  > class(dates$v1)
> [1] "factor"
>  > class(dates$v2)
> [1] "factor"
>
>   
What about chron library:

dts <- dates(c("02/27/92", "02/27/92", "01/14/92",
               "02/28/92", "02/01/92"))
dts
# [1] 02/27/92 02/27/92 01/14/92 02/28/92 02/01/92
tms <- times(c("23:03:20", "22:29:56", "01:03:30",
               "18:21:03", "16:56:26"))
tms
# [1] 23:03:20 22:29:56 01:03:30 18:21:03 16:56:26
x <- chron(dates = dts, times = tms)
x
# [1] (02/27/92 23:03:19) (02/27/92 22:29:56) (01/14/92 01:03:30)
# [4] (02/28/92 18:21:03) (02/01/92 16:56:26)

# We can add or subtract scalars (representing days) to dates or
# chron objects:
c(dts[1], dts[1] + 10)
# [1] 02/27/92 03/08/92
dts[1] - 31
# [1] 01/27/92


Knut