Global vs. local assignment operators in R (‘<<-’ vs. ‘<-’)
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Understanding the difference between local and global assignment operators in R can be tricky to get your head around. Here’s an example which should clear things up.
First, let’s create two variables named “global_var” and “local_var” and give them the values “global” and “local”, respectively. Notice we are using the standard assignment operator “<-” for both variables.
global_var <- 'global' local_var <- 'local' global_var # RETURNS: 'global' local_var # RETURNS: 'local'
Next, let’s create a function to test out the global assignment operator (“<<-”). Inside this function, we will assign a new value to both of the variables we just created; however, we will use the “<-” operator for the local_var and the “<<-” operator for the global_var so that we can observe the difference in behavior.
my_function <- function() { global_var <<- 'na' local_var <- 'na' print(global_var) print(local_var) } my_function() # RETURNS: # 'na' # 'na'
This function performs how you would expect it to intuitively, right? The interesting part comes next when we print out the values of these variables again.
global_var # RETURNS: 'na' local_var # RETURNS: 'local'
From this result, we can see the difference in behavior caused by the differing assignment operators. When using the “<-” operator inside the function, it’s scope is limited to just the function that it lives in. On the other hand, the “<<-” operator has the ability to edit the value of the variable outside of the function as well.
Global vs. local assignment operators in R (‘<<-’ vs. ‘<-’) was originally published in Trevor French on Medium, where people are continuing the conversation by highlighting and responding to this story.
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