How to Loop Through List in R (3 Examples)

You can use one of the following methods to loop through a list in R:

Method 1: Loop Through List & Display All Sub-Elements on Same Line

for (i in my_list) {
  print(i)
}

Method 2: Loop Through List & Display All Sub-Elements on Different Lines

for (i in my_list) {
  for(j in i)
  {print(j)}
}

Method 3: Loop Through List & Only Display Specific Values

#only display first value in each element of list
for(i in 1:length(my_list)) {
  print(my_list[[i]][1])
}

The following examples show how to use each of these methods with the following list in R:

#create list
team_info <- list(team = 'Mavericks',
                  positions = c('G', 'F', 'C'),
                  all_stars = 3)

#view list
team_info

$team
[1] "Mavericks"

$positions
[1] "G" "F" "C"

$all_stars
[1] 3

Example 1: Loop Through List & Display All Sub-Elements on Same Line

The following code shows how to loop through the list and display each sub-element on the same line:

#print each sub-element on same line
for (i in team_info) {
  print(i)
}

[1] "Mavericks"
[1] "G" "F" "C"
[1] 3

Notice that each sub-element is printed on the same line.

Example 2: Loop Through List & Display All Sub-Elements on Different Lines

The following code shows how to loop through the list and display each sub-element on different lines:

#print each sub-element on different lines
for (i in team_info) {
  for(j in i)
  {print(j)}
}

[1] "Mavericks"
[1] "G"
[1] "F"
[1] "C"
[1] 3

Notice that each sub-element is printed on its own line.

Example 3: Loop Through List & Only Display Specific Values

The following code shows how to loop through the list and display each sub-element on different lines:

#only display first value in each element of list
for(i in 1:length(team_info)) {
  print(team_info[[i]][1])
}

[1] "Mavericks"
[1] "G"
[1] 3

Notice that only the first value in each element of the list is displayed.

Note: Simply change the [1] to display a different value in each element. For example, you could use [2] to display only the second value in each element.