[R] need help in if else condition

Mon Jul 15 01:53:08 CEST 2019

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.