how to order POSIXt objects ?
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
<ripley at 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_cooke at 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.
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-- Jim Holtman Data Munger Guru What is the problem that you are trying to solve?
______________________________________________ R-help at 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, ? ? ? ? ? ? ? ? ?ripley at 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?