question about POSIXct conversion
"character" is a mode
"POSIXct" is a class, but you want c("POSIXt", "POSIXct")
Try
mt <- structure(mt, class=c("POSIXt", "POSIXct"))
or
mt + ISOdatetime(1970,1,1,0,0,0)
or several other such tricks.
On Thu, 5 Jun 2003, Kosenkov Kirill wrote:
Hello! I am trying to compute minimal time on some data like this: mt<-tapply(mrsh$time1,list(mrsh$var1,mrsh$var2),min): a b 145 1054800600 1054789800 340 1054804500 1054794600 349 1054820400 1054792800 55 1054800600 1054789200 57 1054814100 1054791000 78 1054822200 1054790400 843 1054807200 1054795800 864 1054813800 1054790700 92 1054789500 1054790100 940 1054800600 1054795800 971 1054783800 1054796700 where time1 is POSIXct object. str(mt) tells me, that mt has mode 'numeric' NOT POSIXct When i am trying to set: mode(mt)<-'POSIXct' i get a message: Don't know how to convert `structure(c(1054800600, 1054804500, ' to class "POSIXct" When i am trying to do: mode(mt)<-'character' everything is ok. I've tried: class(mt)<-'POSIXct' but matrix structure seems to be lost. How to convert the numeric result of tapply on POSIXct object (with 'min') to POSIXct again??? Thanks!
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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