try xts package and functions: reclass period.max period.min
best, daniel 2011/2/8 Mike Williamson <this.is....@gmail.com> > Hello, > > This is mostly to developers, but in case I missed something in my > literature search, I am sending this to the broader audience. > > > - Are there any plans in the works to make "time" classes a bit more > friendly to the rest of the "R" world? I am not suggesting to allow for > fancy functions to manipulate times, per se, or to figure out how to > properly "add" times or anything complicated. Just some fixes to make it > easier to work with the "time" classes. Here is a sampling of some > strange > bugs with the time classes that, to my knowledge, don't exist with any > other > core classes: > 1. you cannot "unlist" a time without losing the class. E.g., if you > unlist "2010-12-14 20:25:40" (POSIXct), you get "1292387141", at > least on my > OS & with my time zone. Regardless of the exact number, unlisting a > time > class converts it to a numeric. > - upon converting to a numeric, it seems there is an underlying, > assumed origin of "1970-01-01 00:00:00". However, this same > assumption does > not underlie the conversion *back* to a POSIX time, e.g., through > as.POSIXct() function. Therefore, whenever a time is > "accidentally" > converted to a numeric, I have to force it back to a time through > as.POSIXct(), *providing my own details* as to the origin. There > is no easy way to find the underlying origin. This makes me > nervous for any > persistent functions I create. If the underlying origin ever > changes, then > all this code will be inaccurate. Maybe the origin will > never change, but > regardless it makes more sense to allow for the same underlying > origin > default for "as.POSIXct" that is used when unlisting, or > similar activities > that force the time into a numeric. > 2. you cannot perform functions that otherwise seem trivial, such > as a "max" or "min". I understand why, for instance, adding is > hard. But > what about max or min? Greater than or less than are possible, as is > order(). I have my own simple scripts using these 2 functions > in order to > create a "max" & "min" for times, but it would be nice to have > something > vetted & official. > > If others could chime in with any strange behaviors they've seen in > working with times, maybe we could get a critical mass of issues that are > worthy of an overhaul. > > Thanks & Regards, > Mike > > > "Telescopes and bathyscaphes and sonar probes of Scottish lakes, > Tacoma Narrows bridge collapse explained with abstract phase-space maps, > Some x-ray slides, a music score, Minard's Napoleanic war: > The most exciting frontier is charting what's already here." > -- xkcd > > -- > Help protect Wikipedia. Donate now: > http://wikimediafoundation.org/wiki/Support_Wikipedia/en > > [[alternative HTML version deleted]] > > ______________________________________________ > r-de...@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ 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.
