On Tue, Jun 8, 2010 at 11:53 PM, Worik R <wor...@gmail.com> wrote: > Given the following snippet.... > m.nf.xts <- xts(rep(0, length(index(m.xts))), order.by=index(m.xts)) > > Does R know to cache the index(m.xts) or is it more efficient to say... > > m.i <- index(m.xts) > m.nf.xts <- xts(rep(0, length(m.i)), order.by=index(m.i)) this is one call less to a function, and hence more efficient. I suppose it has to be order.by=m.i
Btw, How should R know what to cache? If it would cache all calculations, you'd be out of memory in no time. If you have more questions like this, you can test it by yourself, eg : > x <- sample(rnorm(100)) > id <- index(x) # is in this case equivalent to 1:100 > system.time(replicate(10^5,{rep(0,length(index(x)))[index(x)]})) user system elapsed 7.61 0.09 7.76 > system.time(replicate(10^5,{rep(0,length(id))[id]})) user system elapsed 1.49 0.06 1.58 Cheers Joris > > ? > > cheers > Worik > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@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. > -- Joris Meys Statistical consultant Ghent University Faculty of Bioscience Engineering Department of Applied mathematics, biometrics and process control tel : +32 9 264 59 87 joris.m...@ugent.be ------------------------------- Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php ______________________________________________ R-help@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.