[R] R equiv of #ifdef?

Kurt Hornik Kurt.Hornik at ci.tuwien.ac.at
Mon Jun 7 11:44:58 CEST 1999

>>>>> Bill Simpson writes:

> I was wondering if R has an equivalent of #ifdef.
> I want the code to check if a function has been sourced in yet, and if
> not, then source it in. (I know of replace(), which works for
> packages/libraries)

> Here is what I have come up with.

> my.objects<-objects()
> if(my.objects[my.objects=="thingy2"]!="thingy2")
> 	source("~/papers/speed/junk.r")

> junk.r contains the code for function thingy2().
> This doesn't work: "missing value where logical needed"
> The error message puzzles me.

>> my.objects[my.objects=="thingy2"]!="thingy2"
> logical(0)

> Thanks very much for any help.

Try exists().

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