Dear Everybody, Thanks, length() is the answer.
Best, Jay On Mon, Nov 24, 2008 at 1:15 PM, Ted Harding <[EMAIL PROTECTED]> wrote: > On 24-Nov-08 17:41:25, G. Jay Kerns wrote: >> Dear R-help, >> I first thought that the empty set (for a vector) would be NULL. >> >> x <- c() >> x >> >> However, the documentation seems to make clear that there _many_ empty >> sets depending on the vector's mode, namely, numeric(0), character(0), >> logical(0), etc. This is borne out by >> >> y <- letters[1:3] >> z <- letters[4:6] >> intersect(y,z) >> >> which, of course, is non-NULL: >> >> is.null(character(0)) # FALSE > > In the above (and below) cases, would not > > (length(x)==0) > > do? > Ted. > >> So, how can we test if a vector is, say, character(0)? The following >> doesn't (seem to) work: >> >> x <- character(0) >> x == character(0) # logical(0) >> >> More snooping led to the following: >> >> wiki.r-project.org/rwiki/doku.php?id=tips:surprises:emptysetfuncs >> >> and at the bottom of the page it says "logical(0) is an empty set, >> thus is TRUE". However, I get >> >> isTRUE(logical(0)) # FALSE >> >> but, on the other hand, >> >> all.equal(x, character(0)) # TRUE >> >> This would seem to be the solution, but am I missing something? and in >> particular, is there an elegant way to check in the case that the mode >> of the vector is not already known? >> >> Thanks in advance for any insight you may have. >> >> Best, >> Jay > > -------------------------------------------------------------------- > E-Mail: (Ted Harding) <[EMAIL PROTECTED]> > Fax-to-email: +44 (0)870 094 0861 > Date: 24-Nov-08 Time: 18:15:31 > ------------------------------ XFMail ------------------------------ > -- *************************************************** G. Jay Kerns, Ph.D. Associate Professor Department of Mathematics & Statistics Youngstown State University Youngstown, OH 44555-0002 USA Office: 1035 Cushwa Hall Phone: (330) 941-3310 Office (voice mail) -3302 Department -3170 FAX E-mail: [EMAIL PROTECTED] http://www.cc.ysu.edu/~gjkerns/ ______________________________________________ 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.
