Hi r-help-boun...@r-project.org napsal dne 17.01.2011 15:59:37:
> 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. I have no idea what is regular week. Seems to me that you seek some rolling maxima for which I suggest to consult package zoo and its function rollapply. > 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]] cbind binds together three vectors and makes a matrix. Matrix can have only values of only one type. Therefore it strips off days to underlying numeric representation. If you want to know more about R objects and their properties you could read R intro. > str(cbind(days,price,regular)) num [1:70, 1:3] 14991 14990 14989 14988 14987 ... - attr(*, "dimnames")=List of 2 ..$ : NULL ..$ : chr [1:3] "days" "price" "regular" Regards Petr > > ______________________________________________ > 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. ______________________________________________ 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.
