[R] finding global variables in a function containing formulae

[Gabor Grothendieck]

On Thu, Nov 1, 2012 at 2:04 PM, Hafen, Ryan P <Ryan.Hafen at pnnl.gov> wrote:
> I need to find all global variables being used in a function and findGlobals() in the codetools package works quite nicely.  However, I am not able to find variables that are used in formulae.  Simply avoiding formulae in functions is not an option because I do not have control over what functions this will be applied to.
>
> Here is an example to illustrate:
>
> library(codetools)
>
> xGlobal <- rnorm(10)
> yGlobal <- rnorm(10)
>
> plotFn1 <- function() {
>    plot(yGlobal ~ xGlobal)
> }
>
> plotFn2 <- function() {
>    y <- yGlobal
>    x <- xGlobal
>    plot(y ~ x)
> }
>
> plotFn3 <- function() {
>    plot(xGlobal, yGlobal)
> }
>
> findGlobals(plotFn1, merge=FALSE)$variables
> # character(0)
> findGlobals(plotFn2, merge=FALSE)$variables
> # [1] "xGlobal" "yGlobal"
> findGlobals(plotFn3, merge=FALSE)$variables
> # [1] "xGlobal" "yGlobal"
>
> I would like to find that plotFn1 also uses globals xGlobal and yGlobal.  Any suggestions on how I might do this?

If this is only being applied to your own functions then we can have a
convention when writing them to help it in which we "declare" such
variables so that findGlobals can locate them:


plotFn1 <- function() {
   xGlobal; yGlobal
   plot(yGlobal ~ xGlobal)
}

findGlobals(plotFn1)

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