Re: [R] problem with unlist POSIX date at midnight

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Wed 17 Jan 2007 - 10:12:58 GMT

On Wed, 17 Jan 2007, Hanneke Schuurmans wrote:

> Dear R-users,
>
> I use unlist of POSIX dates to extract the year, hour etc. With that I
> can search for files in my database which are in the form
> 'yyyymmddhh_synops.txt'
> However, I get stucked during midnight where unlist just gives NA's.
> The script is given below, the problem accurs at acc.period[16]
> (midnight). However when I write out the character, unlist works well.
> But as.character(acc.period[16]) is not the solution....
>
> begin=paste(dates[i]-1,"09:00:00")
> end=paste(dates[i],"08:00:00")
> acc.period=seq(as.POSIXct(begin),as.POSIXct(end),"hour")
>
> unlist(strptime(acc.period[16],format="%Y-%m-%d %H:%M:%S"))
> # sec min hour mday mon year wday yday isdst
> # NA NA NA NA NA NA NA NA -1
> unlist(strptime(acc.period[17],format="%Y-%m-%d %H:%M:%S"))
> # sec min hour mday mon year wday yday isdst
> # 0 0 1 1 2 106 3 59 0
>
> a="2006-03-01 00:00:00"
> unlist(strptime(a,format="%Y-%m-%d %H:%M:%S"))
> # sec min hour mday mon year wday yday isdst
> # 0 0 0 1 2 106 3 59 0
>
> Could someone help?

Please see the footer comment

> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

We do need that to help you. Using unclass() rather than unlist() will help us see what strptime actually returned (I suspect the NAs are from there as your (unshown) input was invalid, e.g. had hour=24).

We also need the other information the posting guide asks for, such as the output of sessionInfo().

-- 
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

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Received on Wed Jan 17 21:18:27 2007

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