[R] switch and factors

[Allan Engelhardt]

Maybe I am misunderstanding you, but I think it is documented?  The help 
page says

switch(EXPR, ...)
[...]
If the value of ‘EXPR’ is not a character string it is coerced to
integer. [...]


Since

is.character( factor('x', levels=c('y', 'x')) )
[1] FALSE


you get

>  as.integer( factor('x', levels=c('y', 'x')) )
[1] 2


from the "coerced to integer" part?  Therefore the second statement (y) 
is evaluated regardless of the label ("y"=).

Allan

On 09/03/11 02:02, baptiste auguie wrote:
> Dear list,
>
> Reading the help page for ?switch didn't give me more than a hint at
> what's going on here,
>
> x = 5
> y = 2
>
> foo<- function(a="x"){
>       switch(a, "x" = x,
>                       "y" = y)
> }
>
> foo(factor('x', levels=c('y', 'x')))
>
> # 2
>
> It seems that switch, when given a factor, uses the numeric codes
> rather than the string levels as I would have naively expected. Is
> this deliberate, should it be mentioned on the help page? I had an
> input that had been invisibly converted to a factor by data.frame();
> using switch resulted in serious confusion.
>
> Thanks,
>
> baptiste
>
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