Re: [R] How to get back POSIXct format after calculating with hist() results

From: <Peter.Marx_at_knorr-bremse.com>
Date: Sat 26 Aug 2006 - 02:03:14 EST


yep, it works!

impressingly elegant. R seems worth to dig into the details. I'll try harder.

Thank You very much

Peter

-----Ursprüngliche Nachricht-----
Von: Prof Brian Ripley [mailto:ripley@stats.ox.ac.uk] Gesendet: Freitag, 25. August 2006 17:53 An: Marx Peter
Cc: r-help@stat.math.ethz.ch
Betreff: Re: [R] How to get back POSIXct format after calculating with hist() results

On Fri, 25 Aug 2006, Peter.Marx@knorr-bremse.com wrote:

> Hi,
>
> I have a casting/formatting question on hist.POSIXt:
>
> The histogram plot from POSIXct works perfect (with help of Prof.
> Ripley -thanks!). When processing the hist(plot=FALSE) output and then
> plotting the results over the x-axis (bins) coming from hist(), I lose
> the date/time labels, getting instead integers displayed.
>
> Trying to cast the $breaks with as.POSIXct gives silly results with
> StarTrek-like years.

But you actually called as.POSIXct(as.Date()) on them, which was `silly'.

class(login_bins$mids) <- class(logins$DateTime)

should do the trick.

> What is the proper way to get back the old YY-MM-DD hh:mm:ss labels ?
>
> Peter
>
>
>
> > str(logins)
> `data.frame': 25792 obs. of 1 variable:
> $ DateTime:'POSIXct', format: chr "2006-08-01 00:00:02" "2006-08-01
> 00:00:25" "2006-08-01 00:00:41" ...
>
> > login_bins<-hist(samples$DateTime, "hours", freq=TRUE,plot=FALSE)

>
> > str(login_bins)

> List of 7
> $ breaks : num [1:337] 1.15e+09 1.15e+09 1.15e+09 1.15e+09 1.15e+09
> ...
> $ counts : int [1:336] 6 10 45 25 40 87 257 356 309 214 ...
> $ intensities: num [1:336] 0.000233 0.000388 0.001744 0.000969
> 0.001550 ...
> $ density : num [1:336] 6.46e-08 1.08e-07 4.85e-07 2.69e-07 4.31e-07
> ...
> $ mids : num [1:336] 1.15e+09 1.15e+09 1.15e+09 1.15e+09 1.15e+09
> ...
> $ xname : chr "logins$DateTime"
> $ equidist : logi TRUE
> - attr(*, "class")= chr "histogram"
>
> ... Then I do some calculations with the login_bins$counts, resulting
> in a new vector:
>
> >str(userabs)
> int [1:336] 1 -3 34 39 68 127 347 641 844 943 ...
>
> When I now plot this y over the x-axis coming from the previous
> histogram x-axis with
>
> >plot(login_bins$mids, userabs)

>
> I get the x-axis of labelled with the nums 1154400000, 1154800000...
> (number of seconds since 1970 ?)
>
> Trying to convert this gives funny results.
>
> >as.POSIXct(as.Date(login_bins$mids[1]))
> [1] "2568-10-12 02:00:00 W. Europe Daylight Time"
>
> > as.POSIXct(as.Date(login_bins$mids[2]))
> [1] "2578-08-21 02:00:00 W. Europe Daylight Time"
>
> ______________________________________________
> R-help@stat.math.ethz.ch 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@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

______________________________________________
R-help@stat.math.ethz.ch 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.
Received on Sat Aug 26 02:22:41 2006

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.1.8, at Sat 26 Aug 2006 - 04:24:22 EST.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.