In R, a constant list is a list whose values cannot be changed after it has been created. Constant lists can be created using the list function with the argument constant = TRUE. Here is an example:
# Create a constant list
my_list <- list(a = 1, b = 2, c = 3, constant = TRUE)
# Access values in a constant list
my_list$a # 1
my_list$b # 2
my_list$c # 3
# Attempt to change a value in a constant list
# This will result in an error because the list is constant
my_list$a <- 4
# Error: replacement has length zero
In the above example, we create a constant list called my_list with three entries a, b, and c. We set the constant argument to TRUE to make the list constant. We can access the values in the list using the $ notation.
However, if we try to change the value of the a entry using the <- assignment operator, we will get an error message because the list is constant and cannot be changed.