I have a project in R where I am creating a variety of functions and I have a set of constants that I use in a lot of these functions.
How can I define global variables so they are used across all of my functions? Currently I have to redefine them every time.
Would creating a function for each constant work? Or can I create some kind of constants file and load that in?
That depends. If you're simply using scripts, I believe the best way would be to have a "main" script that calls the others and create a global variable (your "constant"). Something like:
global_constant <<- 12345
However, if you're developing an R package, consider creating a function that uses the R options and defines such behavior when the package is loaded. As described here:
.onLoad <- function(libname, pkgname) {
options(var1='blablabla', var2=12345)
}