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As the name suggests, Global Variables can be accessed from any part of the program.
Example of Global Variable in C You can notice that in line 4, x and y get declared as two of the global variables of the type int. Here, the variable x will get initialized automatically to 0. Then one can use variables like x and y inside any of the given functions.
Global environment can be referred to as . GlobalEnv in R codes as well. We can use the ls() function to show what variables and functions are defined in the current environment. Moreover, we can use the environment() function to get the current environment.
The global Keyword Normally, when you create a variable inside a function, that variable is local, and can only be used inside that function. To create a global variable inside a function, you can use the global keyword.
As Christian's answer with assign() shows, there is a way to assign in the global environment. A simpler, shorter (but not better ... stick with assign) way is to use the <<- operator, ie
a <<- "new"
inside the function.
I found a solution for how to set a global variable in a mailinglist posting via assign:
a <- "old"
test <- function () {
assign("a", "new", envir = .GlobalEnv)
}
test()
a # display the new value
What about .GlobalEnv$a <- "new" ? I saw this explicit way of creating a variable in a certain environment here: http://adv-r.had.co.nz/Environments.html. It seems shorter than using the assign() function.
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