Numerical instability in new R Windows development version
On Jan 27, 2012, at 13:23 , Hans W Borchers wrote:
(1 - (x^2 + y^2)) * (x^2 + y^2 <= 1) It appears to be an often used trick in numerical analysis. One advantage is that a function using it is immediately vectorized while an expression such as, e.g., "max(0, 1 - (x^2 + y^2))" is not.
However, "pmax(0, 1 - (x^2 + y^2))" is (unless 0-length x,y is an issue). But of course, Duncan is right: It is a bug if you can't take the square root of negative zero.
Peter Dalgaard, Professor Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com