Thanks. I did not even know about that function; will have to use it in the future. That is the good news/bad news about R; so many things to learn about.
On Mon, Feb 14, 2011 at 11:58 AM, Prof Brian Ripley <rip...@stats.ox.ac.uk> wrote: > See the help page for order. It has a similar example, and the general > solution is to use xtfrm, not unclass. > > On Mon, 14 Feb 2011, jim holtman wrote: > >> 'unclass' it first(assuming that it is POSIXct) >> >> -unclass(mytime) >> >> On Mon, Feb 14, 2011 at 3:55 AM, JonC <jon_d_co...@yahoo.co.uk> wrote: >>> >>> I have a problem ordering by descending magnitude a POSIXt object. Can >>> someone help please and let me know how to work around this. My goal is >>> to >>> be able to order my data by DATE and then by descending TIME. >>> >>> I have tried to include as much info as possible below. The problem stems >>> from trying to read in times from a CSV file. I have converted the >>> character >>> time values to a POSIXt object using the STRPTIME function. I would like >>> ideally to sort using the order function as below. >>> >>> test.sort <- order(test$DATE, -test$mytime) >>> >>> However, when I try this I receive the error as below : >>> >>> Error in `-.POSIXt`(test2$mytime) : >>> unary '-' is not defined for "POSIXt" objects >>> >>> To make this easier to understand I have pasted my example data below >>> with a >>> list of R commands I have used. Any help or assistance would be >>> appreciated. >>> >>>> test2 <- read.csv("C:/Documents and Settings/Jonathan Cooke/My >>>> Documents/Downloads/test2.csv", sep=",") >>>> test2 >>> >>> DATE TIME >>> 1 18/01/2011 08:00:01 >>> 2 18/01/2011 08:10:01 >>> 3 18/01/2011 08:20:01 >>> 4 18/01/2011 08:30:01 >>> 5 19/01/2011 08:00:01 >>> 6 19/01/2011 08:10:01 >>> 7 19/01/2011 08:20:01 >>> 8 19/01/2011 08:30:01 >>> >>>> test2$mytime <- strptime(test2$TIME,"%H:%M:%S") >>>> test2$mytime >>> >>> [1] "2011-02-14 08:00:01" "2011-02-14 08:10:01" "2011-02-14 08:20:01" >>> "2011-02-14 08:30:01" "2011-02-14 08:00:01" >>> [6] "2011-02-14 08:10:01" "2011-02-14 08:20:01" "2011-02-14 08:30:01" >>> >>>> test2 >>> >>> DATE TIME mytime >>> 1 18/01/2011 08:00:01 2011-02-14 08:00:01 >>> 2 18/01/2011 08:10:01 2011-02-14 08:10:01 >>> 3 18/01/2011 08:20:01 2011-02-14 08:20:01 >>> 4 18/01/2011 08:30:01 2011-02-14 08:30:01 >>> 5 19/01/2011 08:00:01 2011-02-14 08:00:01 >>> 6 19/01/2011 08:10:01 2011-02-14 08:10:01 >>> 7 19/01/2011 08:20:01 2011-02-14 08:20:01 >>> 8 19/01/2011 08:30:01 2011-02-14 08:30:01 >>> >>>> test2.sort <- order(test2$DATE, -test2$mytime) >>> >>> Error in `-.POSIXt`(test2$mytime) : >>> unary '-' is not defined for "POSIXt" objects >>> >>> It's at this stage where I have got stuck as I'm new to R and don't yet >>> know >>> a way of getting around this error. Thanks in advance. >>> >>> JonC >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> -- >>> View this message in context: >>> http://r.789695.n4.nabble.com/how-to-order-POSIXt-objects-tp3304609p3304609.html >>> Sent from the R help mailing list archive at Nabble.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. >>> >> >> >> >> -- >> Jim Holtman >> Data Munger Guru >> >> What is the problem that you are trying to solve? >> >> ______________________________________________ >> 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. >> > > -- > Brian D. Ripley, rip...@stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 -- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? ______________________________________________ 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.