try this:

> x <- data.frame(day=rep(1:10, each=4), site=rep(sample(101:104, 10, TRUE),
each=4))
> s.f <- function(start){
+     start <- start[1] + 0:3  # generate the sequence
+     ifelse(start > 104, start - 4, start)
+ }
> x$siteNew <- ave(x$site, x$day, FUN=s.f)
> x
   day site siteNew
1    1  104     104
2    1  104     101
3    1  104     102
4    1  104     103
5    2  101     101
6    2  101     102
7    2  101     103
8    2  101     104
9    3  103     103
10   3  103     104
11   3  103     101
12   3  103     102
13   4  101     101
14   4  101     102
15   4  101     103
16   4  101     104
17   5  102     102
18   5  102     103
19   5  102     104
20   5  102     101
21   6  102     102
22   6  102     103


On Mon, Mar 15, 2010 at 1:45 PM, Hosack, Michael <mhosack@state.pa.us>wrote:

> Hey folks,
>
> I have a difficult (at least for me) problem that I was hoping
> one of you may know how to solve. I want to assign a sequence
> to subsets of a variable in a data frame based on date.
> The variable is 'SITE1' and the date is a unique day (DD) and
> month (MM) combination. The sequence contains site numbers 101:104,
> and each day-month combination takes four site numbers from that
> sequence in an order dependent upon which site number is listed.
> For example, I need a sequence of 101,102,103,104 if 101 is the
> number listed, 102,103,104,101 if 102 is the number listed, 104,101,
> 102,103 if the 104 is the number listed for a given DD MM combination,
> etc. As a further example, for every sequence that happens to be
> 102,102,102,102
> for a MM DD combination I want to replace it with 102,103,104,101.
> Please see the attached partial dataframe. Any help would be
> greatly appreciated. I have tried creating a function using seq()
> and then using ddply, and also writing a loop with no luck.
>
> Mike
>
> ______________________________________________
> 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<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

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