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....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
