[R] inefficient ifelse() ?

[ivo welch]

dear R experts---

  t <- 1:30
  f <- function(t) { cat("f for", t, "\n"); return(2*t) }
  g <- function(t) { cat("g for", t, "\n"); return(3*t) }
  s <- ifelse( t%%2==0, g(t), f(t))

shows that the ifelse function actually evaluates both f() and g() for
all values first, and presumably then just picks left or right results
based on t%%2.  uggh... wouldn't it make more sense to evaluate only
the relevant parts of each vector and then reassemble them?

/iaw
----
Ivo Welch