Proposal unary - operator for factors
Currently, for numeric a you can do either ? order(-a) or ? order(a, decreasing=FALSE) For nonnumeric types like POSIXct and factors only the latter works. Under my proposal your ? order(a, -b, c, d) would be ? order(a, b, c, d, decreasing=c(FALSE,TRUE,FALSE,TRUE)) and it would work for any ordably class without modifications to any classes.
Why not use ?order(a, -xtfrm(b), c, -xtfrm(d))
That's a good suggestion. You could make it even easier to read with desc <- function(x) -xtfrm(x) order(a, desc(b), c, desc(d)) Could you remind me what xtfrm stands for? Thanks! Hadley