Thanks to all! This is really helpful!
Sincerely, Erin On Jan 17, 2008 12:00 PM, Marc Schwartz <[EMAIL PROTECTED]> wrote: > Erin Hodgess wrote: > > Hi R People: > > > > I'm reading "Statistical Computing with R", by Maria Rizzo, and it's > > really good. > > > > Anyhow, I have a question about something in there. > > > >> u<- runif(5) > >> u > > [1] 0.1177041 0.4271790 0.4601597 0.2204846 0.4051473 > >> #in the book > >> sum(as.integer(u> 0.4)) > > [1] 3 > >> #what I would do > >> sum(u> 0.4) > > [1] 3 > > > > Is one way better than the other, please? > > > > Thanks, > > Erin > > There is additional coercion overhead in the first approach, since > as.integer() is called separately: > > set.seed(1) > > Vec <- sample(c(TRUE, FALSE), 1000000, replace = TRUE) > > > system.time(sum(Vec)) > user system elapsed > 0.004 0.000 0.025 > > > system.time(sum(as.integer(Vec))) > user system elapsed > 0.013 0.019 0.050 > > > To paraphrase a financial quote: A microsecond here, a microsecond there > and pretty soon you are talking about a serious amount of time... ;-) > > HTH, > > Marc Schwartz > > -- Erin Hodgess Associate Professor Department of Computer and Mathematical Sciences University of Houston - Downtown mailto: [EMAIL PROTECTED] ______________________________________________ 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.