Thanks for your validation. Yes Peter's solution is the fastest, faster than the previous one by saving 25% time. It was missed out in my previous testing. Jin
-----Original Message----- From: Pascal Oettli [mailto:kri...@ymail.com] Sent: Wednesday, 4 July 2012 2:07 PM To: Li Jin Cc: r-help@r-project.org Subject: Re: [R] Is it possible to remove this loop? [SEC=UNCLASSIFIED] Le 04/07/2012 12:43, Peter Ehlers a écrit : > On 2012-07-03 17:23, jin...@ga.gov.au wrote: >> Thank you all for providing various alternatives. They are all pretty >> fast. Great help! Based on a test of a dataset with 800,000 rows, the >> time used varies from 0.04 to 11.56 s. The champion is: >>> a1$h2 <- 0 >>> a1$h2[a1$h1=="H"] <- 1 > > Interesting. My testing shows that Petr's solution is about > twice as fast. Not that it matters much - the time is pretty > small in any case. > > a0 <- data.frame(h1 = sample(c("H","J","K"), 1e7, replace = TRUE), > stringsAsFactors = FALSE) > a1 <- a0 > system.time({a1$h2 <- 0; a1$h2[a1$h1 == "H"] <- 1}) > # user system elapsed > # 1.47 0.48 1.96 > a11 <- a1 > > a1 <- a0 > system.time(a1$h2 <- (a1$h1 == "H") * 1) > # user system elapsed > # 0.37 0.17 0.56 > a12 <- a1 > all.equal(a11,a12) > #[1] TRUE > > Peter Ehlers > I got the same result. Petr's solution is the fastest. Good to know it. Pascal Oettli >> Regards, >> Jin >> >> Geoscience Australia Disclaimer: This e-mail (and files transmitted >> with it) is intended only for the person or entity to which it is >> addressed. If you are not the intended recipient, then you have >> received this e-mail by mistake and any use, dissemination, >> forwarding, printing or copying of this e-mail and its file >> attachments is prohibited. The security of emails transmitted cannot >> be guaranteed; by forwarding or replying to this email, you >> acknowledge and accept these risks. > > ______________________________________________ > 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. > Geoscience Australia Disclaimer: This e-mail (and files transmitted with it) is intended only for the person or entity to which it is addressed. If you are not the intended recipient, then you have received this e-mail by mistake and any use, dissemination, forwarding, printing or copying of this e-mail and its file attachments is prohibited. The security of emails transmitted cannot be guaranteed; by forwarding or replying to this email, you acknowledge and accept these risks. ______________________________________________ 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.
