Hi there, I don't know why the following codes are return different results. > ifelse(3 > 2, 1:3, length(1:3)) [1] 1 > if (3 > 2) 1:3 else length(1:3) [1] 1 2 3 Any hints? Best, Jinsong
ifelse is vectorized. On Wed, Dec 13, 2017 at 7:31 AM, Jinsong Zhao <jszhao at yeah.net> wrote:> Hi there, > > I don't know why the following codes are return different results. > > > ifelse(3 > 2, 1:3, length(1:3)) > [1] 1 > > if (3 > 2) 1:3 else length(1:3) > [1] 1 2 3 > > Any hints? > > Best, > Jinsong > > ______________________________________________ > R-help at 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/posti > ng-guide.html > and provide commented, minimal, self-contained, reproducible code. >[[alternative HTML version deleted]]
ifelse returns the "shape" of the first argument In your ifelse the shape of "3 > 2" is a vector of length one, so it will return a vector length one. Avoid "ifelse" until you are very comfortable with it. It can often burn you. On Wed, Dec 13, 2017 at 5:33 PM, jeremiah rounds <roundsjeremiah at gmail.com> wrote:> ifelse is vectorized. > > On Wed, Dec 13, 2017 at 7:31 AM, Jinsong Zhao <jszhao at yeah.net> wrote: > > > Hi there, > > > > I don't know why the following codes are return different results. > > > > > ifelse(3 > 2, 1:3, length(1:3)) > > [1] 1 > > > if (3 > 2) 1:3 else length(1:3) > > [1] 1 2 3 > > > > Any hints? > > > > Best, > > Jinsong > > > > ______________________________________________ > > R-help at 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/posti > > ng-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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]]
On 13/12/2017 10:31 AM, Jinsong Zhao wrote:> Hi there, > > I don't know why the following codes are return different results. > > > ifelse(3 > 2, 1:3, length(1:3)) > [1] 1 > > if (3 > 2) 1:3 else length(1:3) > [1] 1 2 3 > > Any hints?The documentation in the help page ?ifelse and ?"if" explains it pretty clearly. Think of ifelse() as a function with vector inputs and a vector output, and if() as a flow control construction. Duncan Murdoch
Because ifelse is not intended to be an alternative to if ... else. They exist
for different purposes.
(besides the other replies, a careful reading of their help pages, and trying
the examples, should explain the different purposes).
--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
Lab cell 925-724-7509
On 12/13/17, 7:31 AM, "R-help on behalf of Jinsong Zhao"
<r-help-bounces at r-project.org on behalf of jszhao at yeah.net> wrote:
Hi there,
I don't know why the following codes are return different results.
> ifelse(3 > 2, 1:3, length(1:3))
[1] 1
> if (3 > 2) 1:3 else length(1:3)
[1] 1 2 3
Any hints?
Best,
Jinsong
______________________________________________
R-help at 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.