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.
______________________________________________
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.
