"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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> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>
--
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