Four-core AMD E2-7110 running Ubuntu 18.04 LTS. The R version is the latest in the repository: r-base/bionic,bionic,now 3.4.4-1ubuntu1 all [installed]
Why not 3.6? Because when i followed the installation instructions, adding deb https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ to /etc/apt/sources.list, sudo apt update reported W: GPG error: https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 51716619E084DAB9 E: The repository 'https://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. I just repeated the test. > x <- runif(1000000) > y <- runif(1000000) > system.time(ifelse(x<y,x,y)) user system elapsed 0.359 0.043 0.404 > system.time(pmin(x,y)) user system elapsed 0.015 0.008 0.023 > system.time({r<-numeric(1000000);ix <- x < y; r[ix]<-x[ix]; r[!ix]<-y[!ix]; r}) user system elapsed 0.077 0.028 0.105 On Mon, 15 Jul 2019 at 08:00, peter dalgaard <pda...@gmail.com> wrote: > > Er, what version is this? I have (on a late 2010 MB Air!) > > > system.time(ifelse(x < y, x, y)) > user system elapsed > 0.072 0.012 0.085 > > and even > > > system.time({r<-numeric(1000000);ix <- x < y; r[ix]<-x[ix]; r[!ix]<-y[!ix]; r}) > user system elapsed > 0.082 0.053 0.135 > > -pd > > > > On 12 Jul 2019, at 15:02 , Richard O'Keefe <rao...@gmail.com> wrote: > > > > "ifelse is very slow"? Benchmark time. > >> x <- runif(1000000) > >> y <- runif(1000000) > >> system.time(ifelse(x < y, x, y)) > > user system elapsed > > 0.403 0.044 0.448 > >> system.time(y + (x < y)*(x - y)) > > user system elapsed > > 0.026 0.012 0.038 > > > > This appears to be a quality-of-implementation bug. > > > > > > On Thu, 11 Jul 2019 at 04:14, Dénes Tóth <toth.de...@kogentum.hu> wrote: > > > >> > >> > >> On 7/10/19 5:54 PM, Richard O'Keefe wrote: > >>> Expectation: ifelse will use the same "repeat vectors to match the > >> longest" > >>> rule that other vectorised functions do. So > >>> a <- 1:5 > >>> b <- c(2,3) > >>> ifelse(a < 3, 1, b) > >>> => ifelse(T T F F F <<5>>, 1 <<1>>, 2 3 <<2>>) > >>> => ifelse(T T F F F <<5>>, 1 1 1 1 1 <<5>>, 2 3 2 3 2 <<5>>) > >>> => 1 1 2 3 2 > >>> and that is indeed the answer you get. Entirely predictable and > >> consistent > >>> with > >>> other basic operations in R. > >>> > >>> The only tricky thing I see is that R has > >>> a strict vectorised ifelse(logical.vector, some.vector, another.vector) > >>> AND > >>> a non-strict non-vectorised if (logical.scalar) some.value else > >>> another.value > >>> AND > >>> a statement form if (logical.scalar) stmt.1; else stmt.2; > >> > >> Just for the records, there is a further form: > >> `if`(logical.scalar, stmt.1, stmt.2) > >> > >> The main problem with ifelse is that 1) it is very slow, and 2) the mode > >> of its return value can be unintuitive or not too predictable (see also > >> the Value and Warning sections of ?ifelse). One has to be very careful > >> and ensure that 'yes' and 'no' vectors have the same class, because > >> ifelse will not warn you at all: > >>> ifelse(c(TRUE, TRUE), 1:2, LETTERS[1:2]) > >> [1] 1 2 > >>> ifelse(c(TRUE, FALSE), 1:2, LETTERS[1:2]) > >> [1] "1" "B" > >> > >> For options instead of base::ifelse, you might find this discussion > >> helpful: > >> https://github.com/Rdatatable/data.table/issues/3657 > >> > >> > >> Cheers, > >> Denes > >> > >> > >>> > >>> > >>> On Thu, 11 Jul 2019 at 01:47, Eric Berger <ericjber...@gmail.com> wrote: > >>> > >>>> For example, can you predict what the following code will do? > >>>>> a <- 1:5 > >>>>> b <- c(2,3) > >>>>> ifelse( a < 3, 1, b) > >>>> > >>>> > >>>> On Wed, Jul 10, 2019 at 4:34 PM José María Mateos < ch...@rinzewind.org> > >>>> wrote: > >>>> > >>>>> On Wed, Jul 10, 2019, at 04:39, Eric Berger wrote: > >>>>>> 1. The ifelse() command is a bit tricky in R. Avoiding it is often a > >>>> good > >>>>>> policy. > >>>>> > >>>>> You piqued my curiosity, can you elaborate a bit more on this? > >>>>> > >>>>> -- > >>>>> José María (Chema) Mateos || https://rinzewind.org > >>>>> > >>>>> ______________________________________________ > >>>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > >>>>> 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. > >>>>> > >>>> > >>>> [[alternative HTML version deleted]] > >>>> > >>>> ______________________________________________ > >>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > >>>> 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. > >>>> > >>> > >>> [[alternative HTML version deleted]] > >>> > >>> ______________________________________________ > >>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > >>> 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. > >>> > >> > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > 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. > > -- > Peter Dalgaard, Professor, > Center for Statistics, Copenhagen Business School > Solbjerg Plads 3, 2000 Frederiksberg, Denmark > Phone: (+45)38153501 > Office: A 4.23 > Email: pd....@cbs.dk Priv: pda...@gmail.com > > > > > > > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
