On Fri, 5 Mar 2010, 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, sin!
ce!
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 I understand correctly, then you can easily do the following:
- create a "Date" object with YR-MM-DD
- compute the number of days since origin (2010-04-30 in your case)
- compute integer division by 7 plus 1
In one step:
as.numeric(as.Date(paste(YR, MM, DD, sep = "-")) -
as.Date("2010-04-30")) %/% 7 + 1
BTW: Some of the rest of your information (like DOW) could also be easily
inferred from the "Date", e.g., via transformation to POSIXlt:
as.POSIXlt(as.Date("2010-05-01"))$wday
hth,
Z
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
. . . . . . . .
. . .
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
