That's generally my reaction to them, but you should also read "R News 4/1 -- Help Desk" (http://cran.r-project.org/doc/Rnews/Rnews_2004-1.pdf) which gives some tips on Date()s and the various time classes.
Best, Michael On Thu, Mar 29, 2012 at 2:19 PM, Steven R Corsi <srco...@usgs.gov> wrote: > Thanks very much for the response. That was a very good article and gives me > a good appreciation for the history and covers the structure of the two > date/time formats well. > > What I was specifically looking for is a feel for the situations when one > format should be used over the other. In my work, I have gotten the > impression that I should just use POSIXct for general useability in > functions and graphics until I need to extract specific date components such > as month, day, year, etc. In those instances, just convert to POSIXlt and > extract needed info. Is this mostly accurate? More generally, is there a > resource that summarizes which date/time objects to use under which > conditions? So far, I have mostly been learning by trial/error/web searching > which eventually is effective, but can be quite slow. > > Thanks > Steve > > =============================================== > Steven R. Corsi Phone: (608) 821-3835 > Research Hydrologist email: srco...@usgs.gov > U.S. Geological Survey > Wisconsin Water Science Center > 8505 Research Way > Middleton, WI 53562 > =============================================== > > > > On 3/28/2012 12:16 PM, Duncan Murdoch wrote: >> >> On 28/03/2012 10:06 AM, Steven R Corsi wrote: >>> >>> Hello R users >>> >>> I am searching for a descriptive summary of the use of POSIXlt as >>> compared to POSIXct date/time formats. I have been using them >>> extensively for different purposes, but still can't quite understand >>> when to use which one for the most efficient coding and use. I typically >>> use them in graphics, comparison of times, interpolation of values >>> between times, computation of time-series parameters, and so on. >>> >>> My request is simply to learn if there is a resource out there that >>> explains the strengths of the use of each format in different situations >>> and if certain situations require one over the other. My web searches >>> have turned up basic things like the vector form (POSIXlt) vs the >>> decimal form (POSIXct), but I could not find specific guidance to >>> understand when it is best to use one over the other. >> >> >> The first of the "Other Topics" among the "Technical Papers" available >> from the main HTML help page in R should address this. >> >> Duncan Murdoch > > > ______________________________________________ > 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.
