Global variables in packages in R

Question

I'm developing a package in R. I have a bunch of functions, some of them need some global variables. How do I manage global variables in packages?

I've read something about environment, but I do not understand how it will work, of if this even is the way to go about the things.

Answer 1

You can use package local variables through an environment. These variables will be available to multiple functions in the package, but not (easily) accessable to the user and will not interfere with the users workspace. A quick and simple example is:

pkg.env <- new.env()

pkg.env$cur.val <- 0
pkg.env$times.changed <- 0

inc <- function(by=1) {
    pkg.env$times.changed <- pkg.env$times.changed + 1
    pkg.env$cur.val <- pkg.env$cur.val + by
    pkg.env$cur.val
}

dec <- function(by=1) {
    pkg.env$times.changed <- pkg.env$times.changed + 1
    pkg.env$cur.val <- pkg.env$cur.val - by
    pkg.env$cur.val
}

cur <- function(){
    cat('the current value is', pkg.env$cur.val, 'and it has been changed', 
        pkg.env$times.changed, 'times\n')
}

inc()
inc()
inc(5)
dec()
dec(2)
inc()
cur()