The same argument would hold for tan(pi/2). I don't say the result 'NaN' is wrong, but I thought, tan(pi*x) and tanpi(x) should give the same result.
Hans Werner On Fri, Sep 9, 2016 at 8:44 PM, William Dunlap <wdun...@tibco.com> wrote: > 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 > > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel