R get object from global environment from function if object exists in global but use different default if not
You can modify your function to check if x exists in the .GlobalEnv and get it from there if it does, otherwise return the default value.
myfunc <- function(x = 30) { if ("x" %in% ls(envir = .GlobalEnv)) { get("x", envir = .GlobalEnv) } else { x }}So if "x" %in% ls(envir = .GlobalEnv) is FALSE it would return
myfunc()[1] 30If x is found it would return it. if x <- 100:
myfunc()[1] 100Edit after comment
If you want to make sure to only return x from the global environment if x is not specified as an argument to myfunc, you can use missing(). It returns TRUE if x was not passed and FALSE if it was:
myfunc <- function(x = 30) { if ("x" %in% ls(envir = .GlobalEnv) & missing(x)) { get("x", envir = .GlobalEnv) } else { x }} So for your example:
x <- 100myfunc(x=300)[1] 300
The simplest method would be to set an appropriate default argument:
myfunc <- function(x=get("x", globalenv()){ x}> x <- 100> f()[1] 100> f(30)[1] 30> rm(x)> f()Error in get("x", globalenv()) : object 'x' not found