On Mar 5, 2010, at 4:23 PM, Hosack, Michael wrote:
Hello everyone,
My progress has stalled on finding a way of creating a somewhat
complicated variable to add to my existing dataframe and I am hoping
one of you could help me out. The dataframe below contains only a
fraction of the data of my complete dataframe, but all of the
variables. What I want to do is add another variable named 'WEEK' to
this dataframe that is assigned 1 for row 1 and remains 1 until the
first SAT (i.e. Saturday) under variable 'DOW' (day of week) occurs,
at which point variable 'WEEK' is now assigned 2. 'WEEK' should
continue to be assigned 2 until the following SAT under variable
'DOW' at which variable 'WEEK' will now be assigned 3, and so on. In
this scheme, weekdays are such that SAT=1, SUN=2, MON=3,.....FRI=7.
I am basically trying to assign week numbers to potential sampling
days in a survey season for use in a program that will generate a
fisheries creel survey schedule. I should note that if element 1
happens to have DOW=SAT (that is the case this year, since!
the first day of our survey 05/01 is a Saturday), then WEEK 1
begins on day 1 (05/01/2010) and WEEK 2 will begin on the first SAT
under variable DOW. I hope I explained this clearly enough, if not
let me know. If this sent twice, I apologize.
Mike
MM DD YR DOW DOW. DTYPE TOD TOD. SITENUM DESC
1 05 01 2010 SAT 1 2 MORN 1
101 WALNUT.CK
185 05 01 2010 SAT 1 2 MORN 1
102 LAMPE
369 05 01 2010 SAT 1 2 MORN 1
103 EAST.AVE
553 05 01 2010 SAT 1 2 MORN 1
104 NORTH.EAST
737 05 01 2010 SAT 1 2 AFTN 2
101 WALNUT.CK
921 05 01 2010 SAT 1 2 AFTN 2
102 LAMPE
1105 05 01 2010 SAT 1 2 AFTN 2
103 EAST.AVE
1289 05 01 2010 SAT 1 2 AFTN 2
104 NORTH.EAST
2 05 02 2010 SUN 2 2 MORN 1
101 WALNUT.CK
186 05 02 2010 SUN 2 2 MORN 1
102 LAMPE
370 05 02 2010 SUN 2 2 MORN 1
103 EAST.AVE
554 05 02 2010 SUN 2 2 MORN 1
104 NORTH.EAST
738 05 02 2010 SUN 2 2 AFTN 2
101 WALNUT.CK
922 05 02 2010 SUN 2 2 AFTN 2
102 LAMPE
1106 05 02 2010 SUN 2 2 AFTN 2
103 EAST.AVE
1290 05 02 2010 SUN 2 2 AFTN 2
104 NORTH.EAST
3 05 03 2010 MON 3 1 MORN 1
101 WALNUT.CK
187 05 03 2010 MON 3 1 MORN 1
102 LAMPE
371 05 03 2010 MON 3 1 MORN 1
103 EAST.AVE
555 05 03 2010 MON 3 1 MORN 1
104 NORTH.EAST
739 05 03 2010 MON 3 1 AFTN 2
101 WALNUT.CK
923 05 03 2010 MON 3 1 AFTN 2
102 LAMPE
1107 05 03 2010 MON 3 1 AFTN 2
103 EAST.AVE
1291 05 03 2010 MON 3 1 AFTN 2
104 NORTH.EAST
4 05 04 2010 TUE 4 1 MORN 1
101 WALNUT.CK
188 05 04 2010 TUE 4 1 MORN 1
102 LAMPE
372 05 04 2010 TUE 4 1 MORN 1
103 EAST.AVE
. . . . . . . .
. . .
You could trunc() the results of this function applied to your dates
and "2010-05-01":
> diffweek <- function(x,y) {difft <- difftime( x , y)/7; attr(difft,
"units") <- "weeks"; difft}
> diffweek(Sys.Date() , as.Date("2010-01-01") )
Time difference of 9 weeks
> diffweek(Sys.Date()+1 , as.Date("2010-01-01") )
Time difference of 9.142857 weeks
There is also a week function in the tis package.
Perhaps (untested):
dfrm$weeknum <- trunc(apply(dfrm, 1, function(x)
diffweek(as.Date(x[4], x[2], x[3], sep="-") ,
as.Date("2010-05-01")
)
) )
--
David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
