[R] to append a column to a data frame, has I use loop/if in my case?

[Joshua Ulrich]

Please do not cross post: http://stackoverflow.com/q/4720076/271616

At the minimum, it would be polite to respond here with the answer you
accepted on Stack Overflow.
--
Joshua Ulrich  |  FOSS Trading: www.fosstrading.com



On Mon, Jan 17, 2011 at 8:59 AM, Daniel Wu <daniel_wu_r at 163.com> wrote:
> days=Sys.Date()-1:70
> price=abs(rnorm(70))
> regular=rep(c(0,0,0,0,1,0,1,0,0,1),c(7,7,7,7,7,7,7,7,7,7))
> y=data.frame(cbind(days,price,regular))
>
>
> y is like
>    days      price regular
> 1  14990 0.16149463       0
> 2  14989 1.69519358       0
> 3  14988 1.57821998       0
> 4  14987 0.47614311       0
> 5  14986 0.87016180       0
> 6  14985 2.55679229       0
> 7  14984 0.89753533       0
>
>
> the output I want:
> have another column appended to y, whose value is the max price in the recent 2 **regular** weeks.
> So if the current row is today, then get the max price of the past 14 days (including today) if the last 2 week are regular weeks,  if one of the last 2 weeks is not regular week, then I need to go back further to find the max price, as I need the max price for the last 2 **regular** weeks. How can I do that? Or I have to use loop/if to do it?
>
>
>
>
> BTW, why the days is like 14990,14989, after cbind(days,price,regular)? before the cbind, days is like the format "2010-12-23".
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.
>