On Sun, Nov 27, 2011 at 4:08 PM, Kevin Burton <rkevinbur...@charter.net> wrote: > I admit it isnt reality but I was hoping through judicious use of these > functions I could approximate reality. For example in the years where there > are more than 53 weeks in a year I would be happy if there were a way to > recognize this and drop the last week of data. If there were less than 53 I > would "pad" the year with an extra dummy week. This is just about the same as > your suggestion of putting more than 7 days in the first and last weeks. But > i still need this kind of date manipulation to even know how many days to add > in to make the approximation viable. This kind of best approximation to > reality seems better than to settle for the resolution of a month just > because it is consistent. Daily would be too much data and even then there > would be an approximation due to leap years. >
OK. As you are willing to regard days past the 364th as part of the last week of the year then we can do this. Create a zoo object z as test data. Then convert its time scale to year + week/52 where 0 is the first week of the year and we replace any week that is greater than 51 with 51. Then we aggregate z by week taking the last data point in the week and convert it to ts. Because of the way we constructed it the frequency will be 52. library(zoo) # test data z <- zoo(1:100, Sys.Date() + 1:100) yr.wk <- with(as.POSIXlt(time(z)), year + 1900 + pmin(yday %/% 7, 51) / 52) z.wk <- aggregate(z, yr.wk, tail, 1) z.ts <- as.ts(z.wk) frequency(z.ts) # 52 -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ 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.
