[R] running functions at fixed times
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Tue Jan 9 08:45:23 CET 2001
On Tue, 9 Jan 2001 detlef.steuer at unibw-hamburg.de wrote:
> I can only speak for the Linux/Unix enviroment:
> system("sleep 60")
> mydata <- read.table(...)
> to update mydata after a 60 second break.
> An alternative is to use "cron" or "at". Both allow the specification
> of exact execution times, while the "while" approach tries to imitate
> a real time system.
There is a Sys.sleep function in R these days. BUT, under that
approach, the R process does nothing but update its internal copy of
.RData, and I don't think that is useful. In particular, nothing can ever
be done with mydata, as nothing else can be run.
What I think Jeff Miller wants is for a task to be run in the background of
the R session to update mydata, while he gets on with some work at the
prompt. That's a lot harder. R is single-threaded and does not have
(user-specified timer) events. Not quite impossible, though, as it does
have an event loop to handle UI events, and one could subvert this by some
The difference between Sys.sleep(60.0) and system("sleep 60") is that the
former keeps the event loop ticking over, and that it works across
Jeff mentioned S. S version 4 does have events and monitors, but I have
never been sure how much of that is operational in S-PLUS 5/6.x.
> Have a nice day
> Detlef Steuer ** Universität der Bw ** 22043 Hamburg
> Tel: (0049) (0)40/6541-2819
> steuer at unibw-hamburg.de
> On 09-Jan-01 Jeff Miller wrote:
> > Is there an easy way to automatically run an R function at fixed
> > intervals of time?
> > For example, if I have a file, mydata.txt, which is updated every
> > minute or so,
> > is there an R or an S function which would execute the command
> > mydata <- read.table("mydata.txt")
> > each minute? Basically I just want "mydata" to be constantly updated
> > without
> > my having to bother with it.
> > Thanks in advance,
> > Jeff Miller
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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 272860 (secr)
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