[R] ifelse

[juli g. pausas]

I suppose this is a very basic question, but I cannot understant it:

> aa <- data.frame(x = c(rep("x", 3), NA, NA, NA), y= 1:6)
> aa$x[4]
[1] <NA>
Levels:  x
> aa$y[4]
[1] 4
> aa$y[4] <- ifelse(aa$x[4]=="x", NA, aa$y[4])
> aa$y[4]
[1] NA
>

I was expecting aa$y[4] not to be changed, but I may missundertood
something.

aa2 <- data.frame(x = c(rep("x", 3), rep("b", 3)), y= 1:6)
aa2$y <- ifelse(aa2$x=="x", NA, aa2$y)

this works OK

(R 1.5.0 on Windows)

juli

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