[R] zero index and lazy evaluation in ifelse()

[Peter Dalgaard]

White.Denis at epamail.epa.gov writes:

> I don't understand this behavior:
> 
> > a <- c(0, 1, 2, 3)
> > b <- c(1, 2, 3, 4)
> > ifelse (a == 0, 0, b[a])
> [1] 0 2 3 1
> 
> rather than the desired 0 1 2 3.  Thanks for any explanation.

b[a] is c(1,2,3), recycling to length 4 gives c(1,2,3,1), get it?

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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