data.frame, data types, and apply

Dear all,

Here is an issue I often stumble on.

1- colunm types in data.frames.

-------------------------------

d <- data.frame(x=as.character(c("a", "b", "c")), y=as.numeric(c(1, 2, 3)))
d

x y
1 a 1
2 b 2
3 c 3

is.numeric(d[1,2])

[1] TRUE

is.numeric(d[1,1])

[1] FALSE

apply(d, c(1,2), is.numeric)

x     y
1 FALSE FALSE
2 FALSE FALSE
3 FALSE FALSE

-------------------------------

All item in column "y" should be TRUE right? What should I do to apply
a function only to numerics in d? (beside using nested 'for' loops)

Thanks for your help, and for all the great software.


Vincent Detours