You are correct in your expectations. This is a bug: the C code does not cover the cases +/-Inf (because it uses R_FINITE to exclude them). I'll fix it in R-patched: filing with R-bugs for the record.
On 20 Jun 2002, Markus [ISO-8859-1] Jäntti wrote:
I am doing work on changes in establishment sizes and came across behavior that is quite understandable and easily worked around but a little surprising. On R 1.5.1 on Debian unstable (see below for R.version output):
cut.off <- c(-Inf, 0, Inf) x <- c(-Inf, -10, 0, 10, Inf) is.numeric(x)
[1] TRUE
is.double(x)
[1] TRUE
# but cut(x, cut.off, include.lowest=T)
[1] <NA> [-Inf,0] [-Inf,0] (0,Inf] <NA> The reason I am surprised is that standard logical operations on Inf generate expected results and storage.mode(Inf) is double and so on, so I was expecteing -Inf to belong to the lowest factor level and Inf to belong the highest. [For what it is worth, I am classifying establishments by their growth across years and one that in t1 has 0 workers and >0 in the next has infinite growth. This is easily worked around, but I am a little curious.] Regards, Markus code: cut.off <- c(-Inf, 0, Inf) x <- c(-Inf, -10, 0, 10, Inf) is.numeric(x) is.double(x) # but cut(x, cut.off, include.lowest=T)
R.version
_ platform i386-pc-linux-gnu arch i386 os linux-gnu system i386, linux-gnu status major 1 minor 5.1 year 2002 month 06 day 17 language R -- Markus Jantti Statistics Finland and University of Tampere markus.jantti@iki.fi http://www.iki.fi/~mjantti -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
Brian D. Ripley, ripley@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._