You can use the following syntax to create an empty list in R:
#create empty list with length of zero empty_list #create empty list of length 10 empty_list list', length=10)
The following examples show how to use these functions in practice.
Example 1: Create Empty List in R with Length of Zero
The following code shows how to create an empty list with a length of zero in R:
#create empty list empty_list #verify that empty_list is of class 'list' class(empty_list) [1] "list" #view length of list length(empty_list) [1] 0
The result is a list with a length of 0.
Example 2: Create Empty List in R with Specific Length
The following code shows how to create an empty list of length 8 in R:
#create empty list of length 8 empty_list list', length=8) #verify that empty_list is of class 'list' class(empty_list) [1] "list" #view list empty_list [[1]] NULL [[2]] NULL [[3]] NULL [[4]] NULL [[5]] NULL [[6]] NULL [[7]] NULL [[8]] NULL
The result is a list with a length of 8 in which every element in the list is NULL.
Example 3: Append Values to Empty List in R
One of the most common reasons to create an empty list is to then fill it with values using a loop.
The following code shows how to create an empty list, then fill it with values:
#create empty list of length 8 empty_list list', length=8) #get length of list len #define values to append to list new #fill values in list i = 1 while(i #display updated list empty_list [[1]] [1] 3 [[2]] [1] 5 [[3]] [1] 12 [[4]] [1] 14 [[5]] [1] 17 [[6]] [1] 18 [[7]] [1] 18 [[8]] [1] 20
Notice that the empty list is now filled with the new values that we specified.
Additional Resources
How to Create an Empty Data Frame in R
How to Append Values to List in R
How to Convert List to Vector in R