Loop Through List in R (Example) | while- & for-Loop Over Lists

In this R programming tutorial you’ll learn how to run a for-loop to loop through a list object.

The tutorial looks as follows:

Let’s start right away:

Introduction of Example Data

Let’s first create some example data in R:

my_list <- list(c(6, 1, 5, 4, 1),    # Create example list
                "XXXX",
                letters[1:3])
my_list                              # Print example list
# [[1]]
# [1] 6 1 5 4 1
# 
# [[2]]
# [1] "XXXX"
# 
# [[3]]
# [1] "a" "b" "c"

The previous output of the RStudio console shows the structure of our example data – It’s a list consisting of three different list elements.

Example: for-Looping Over List Elements in R

In this Example, I’ll explain how to loop through the list elements of our list using a for-loop in R. Within each iteration of the loop, we are printing the first entry of the corresponding list element to the RStudio console:

for(i in 1:length(my_list)) {        # Loop from 1 to length of list
  print(my_list[[i]][1])             # Printing some output
}
# [1] 6
# [1] "XXXX"
# [1] "a"

This example has shown how to loop over a list using a for-loop. However, it would also be possible to loop through a list with a while-loop or a repeat-loop.

Video, Further Resources & Summary

Have a look at the following video of my YouTube channel. I explain the examples of this tutorial in the video.

The YouTube video will be added soon.

Also, you might read some of the other articles on this website.

• Store Results of Loop in List
• Append to List in Loop
• for-Loop in R
• Loops in R
• The R Programming Language

To summarize: In this article, I showed how to loop over list elements in R. Don’t hesitate to tell me about it in the comments below, if you have further questions or comments.