[R] r help date format changes with c() vs. rbind()

[Tim Clark]

Glad to know it isn't just me!  I couldn't use Phil's data.frame method since my real problem went from a POSIXct object to a large matrix where I used rbind and then back to POSIXct.  Jim's function worked great on converting the final product back to the proper date.

Thanks!

Tim


Tim Clark
Department of Zoology 
University of Hawaii


--- On Fri, 2/19/10, jim holtman <jholtman at gmail.com> wrote:

> From: jim holtman <jholtman at gmail.com>
> Subject: Re: [R] r help date format changes with c() vs. rbind()
> To: "Tim Clark" <mudiver1200 at yahoo.com>
> Cc: r-help at r-project.org
> Date: Friday, February 19, 2010, 12:19 PM
> I have used the following function to
> convert to POSIXct from a numeric without any
> problems:
>  
> > unix2POSIXct <- function (time)  
> structure(time, class = c("POSIXt",
> "POSIXct"))
> > 
> > unix2POSIXct(946764000)
> [1] "2000-01-01 17:00:00 EST"
> > 
> 
> 
> 
> 
> On Fri, Feb 19, 2010 at 4:07 PM,
> Tim Clark <mudiver1200 at yahoo.com>
> wrote:
> 
> Dear
> List,
> 
> I am having a problem with dates and I would like to
> understand what is going on.  Below is an example.  I can
> produce a date/time using as.POSIXct, but I am trying to
> combine two as.POSIXct objects and keep getting strange
> results.  I thought I was using the wrong origin, but
> according to structure(0,class="Date") I am not
> (see below).  In my example a is a simple date/time object,
> b combines it using rbind(), c converts b to a date/time
> object again using as.POSIXct and gives the incorrect time,
> and d combines a using c() and gives the correct time.  Why
> doesn't c give me the correct answer?
> 
> 
> Thanks,
> 
> Tim
> 
> 
> > a<-as.POSIXct("2000-01-01 12:00:00")
> > a
> [1] "2000-01-01 12:00:00 HST"
> 
> > b<-rbind(a,a)
> > b
>       [,1]
> a 946764000
> a 946764000
> 
> 
> > c<-as.POSIXct(b,origin="1970-01-01")
> > c
> [1] "2000-01-01 22:00:00 HST"
> [2] "2000-01-01 22:00:00 HST"
> 
> > d<-c(a,a)
> > d
> [1] "2000-01-01 12:00:00 HST"
> 
> [2] "2000-01-01 12:00:00 HST"
> 
> 
> > structure(0,class="Date")
> [1] "1970-01-01"
> 
> 
> Tim Clark
> Department of Zoology
> University of Hawaii
> 
> ______________________________________________
> 
> 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.
> 
> 
> 
> -- 
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
> 
> What is the problem that you are trying to solve?
> 
>