The IEEE floating point standard allows for negative zero, but it's hard to know that you have one in R. One reliable test is to take the reciprocal. For example,
> y <- 0 > 1/y [1] Inf > y <- -y > 1/y [1] -Inf The other day I came across one in complex numbers, and it took me a while to figure out that negative zero was what was happening: > x <- complex(real = -1) > x [1] -1+0i > 1/x [1] -1+0i > x^(1/3) [1] 0.5+0.8660254i > (1/x)^(1/3) [1] 0.5-0.8660254i (The imaginary part of 1/x is negative zero.) As a Friday question: are there other ways to create and detect negative zero in R? And another somewhat more serious question: is the behaviour of negative zero consistent across platforms? (The calculations above were done in Windows in R-devel.) Duncan Murdoch ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
