[R] need help in if else condition

Richard O'Keefe r@oknz @end|ng |rom gm@||@com
Tue Jul 16 15:32:23 CEST 2019 

I didn't communicate my problem to R-Sig-Debian because I had never
previously
heard of them.  Thank you for the tip.
Poking through the recent archives there I see other people
have had (different) trouble with the Bionic repository.

Fortunately, the instructions at
https://linuxize.com/post/how-to-install-r-on-ubuntu-18-04/
worked, after I first removed the existing installation of R.
All I had to do after that was reinstall about 180 packages.
Is there a way to do this automatically?

However, having installed "Action of the Toes" (are R releases named
by Culture AIs, by any chance?) I still find
> x <- runif(1000000)
> y <- runif(1000000)
> system.time(ifelse(x < y, x, y))
   user  system elapsed
  0.087   0.047   0.135
> system.time(y + (x < y)*(x-y))
   user  system elapsed
  0.035   0.008   0.042
> system.time(pmin(x,y))
   user  system elapsed
  0.025   0.004   0.030

On Mon, 15 Jul 2019 at 12:04, Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
wrote:

> Did you ask for assistance on R-Sig-Debian? you will need to be more
> explicit than below about what you actually did. FWIW I was able to do it
> [1]... you might have encountered a temporary network problem.
>
> [1] https://cran.r-project.org/bin/linux/ubuntu/README.html
>
> On July 14, 2019 4:55:25 PM CDT, Richard O'Keefe <raoknz using gmail.com> wrote:
> >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 <pdalgd using 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 <raoknz using 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.denes using 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 <ericjberger using 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 <
> >chema using 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 using 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 using 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 using 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 using 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.mes using cbs.dk  Priv: PDalgd using gmail.com
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >       [[alternative HTML version deleted]]
> >
> >______________________________________________
> >R-help using 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.
>
> --
> Sent from my phone. Please excuse my brevity.
>

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