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R Global Variables


Global Variables

Variables that are created outside of a function are known as global variables.

Global variables can be used by everyone, both inside of functions and outside.

Example

Create a variable outside of a function and use it inside the function:

txt <- "awesome"
my_function <- function() {
  paste("R is", txt)
}

my_function()
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If you create a variable with the same name inside a function, this variable will be local, and can only be used inside the function. The global variable with the same name will remain as it was, global and with the original value.

Example

Create a variable inside of a function with the same name as the global variable:

txt <- "global variable"
my_function <- function() {
  txt = "fantastic"
  paste("R is", txt)
}

my_function()

txt # print txt
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If you try to print txt, it will return "global variable" because we are printing txt outside the function.


The Global Assignment Operator

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 assignment operator <<-

Example

If you use the assignment operator <<-, the variable belongs to the global scope:

my_function <- function() {
txt <<- "fantastic"
  paste("R is", txt)
}

my_function()

print(txt)
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Also, use the global assignment operator if you want to change a global variable inside a function:

Example

To change the value of a global variable inside a function, refer to the variable by using the global assignment operator <<-:

txt <- "awesome"
my_function <- function() {
  txt <<- "fantastic"
  paste("R is", txt)
}

my_function()

paste("R is", txt)
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