It should be the case that tan(pi*x) != tanpi(x) in many cases - that is why it was added. The limits from below and below of the real function tan(pi*x) as x approaches 1/2 are different, +Inf and -Inf, so the limit is not well defined. Hence the computer function tanpi(1/2) ought to return Not-a-Number.
Bill Dunlap TIBCO Software wdunlap tibco.com On Fri, Sep 9, 2016 at 10:24 AM, Hans W Borchers <hwborch...@gmail.com> wrote: > As the subject line says, we get different results for tan(pi/2) and > tanpi(1/2), though this should not be the case: > > > tan(pi/2) > [1] 1.633124e+16 > > > tanpi(1/2) > [1] NaN > Warning message: > In tanpi(1/2) : NaNs produced > > By redefining tanpi with sinpi and cospi, we can get closer: > > > tanpi <- function(x) sinpi(x) / cospi(x) > > > tanpi(c(0, 1/2, 1, 3/2, 2)) > [1] 0 Inf 0 -Inf 0 > > Hans Werner > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel