Avoid for-Loop in R? (Alternatives) | Using lapply Function Instead

 

In this R tutorial you’ll learn how to use the lapply function instead of for-loops.

The article will consist of this content:

If you want to know more about these topics, keep reading…

 

Example 1: Conventional for-Loop in R

In Example 1, I’ll show how to write and run a traditional for-loop in R.

Let’s assume that we want to run five iterations ranging from 1 to 5. In each iteration we want to print a sentence returning the current iteration index of the loop.

For this task, we can use the following R code:

for(i in 1:5) {              # Running for-loop
  print(paste("Iteration No.", i, "Created by for-Loop"))
}
# [1] "Iteration No. 1 Created by for-Loop"
# [1] "Iteration No. 2 Created by for-Loop"
# [1] "Iteration No. 3 Created by for-Loop"
# [1] "Iteration No. 4 Created by for-Loop"
# [1] "Iteration No. 5 Created by for-Loop"

As you can see, the RStudio console returned five sentences showing the index number of each iteration.

This code worked well. However, if not properly used for-loops can get very slow when applied to large data sets or in complex settings such as nested for-loops.

For that reason, it might make sense for you to avoid for-loops and to use functions such as lapply instead. This might speed up the R syntax and can save a lot of computational power!

The next example explains how to use the lapply function in R.

 

Example 2: Using lapply() Function Instead of for-Loop (Fast Alternative)

This Section explains how to create exactly the same output as in Example 1 using the lapply function in combination with the invisible function in R. Have a look at the following R syntax and its output:

invisible(lapply(1:5,        # Using lapply function
                 function(i) {
                   print(paste("Iteration No.", i, "Created by lapply Function"))
                 }
))
# [1] "Iteration No. 1 Created by lapply Function"
# [1] "Iteration No. 2 Created by lapply Function"
# [1] "Iteration No. 3 Created by lapply Function"
# [1] "Iteration No. 4 Created by lapply Function"
# [1] "Iteration No. 5 Created by lapply Function"

Exactly the same as in Example 1! Note that we have used a user-defined function within lapply. In this example, this user-defined function was very simple. However, you may make this function as complex as you want.

 

Video, Further Resources & Summary

Do you need more information on the content of this article? Then you might watch the following video of my YouTube channel. I show the R programming syntax of this tutorial in the video:

 

The YouTube video will be added soon.

 

Furthermore, you might read the other tutorials of this website.

 

To summarize: At this point you should know how to avoid for-loops in the R programming language. Don’t hesitate to let me know in the comments section, if you have any additional comments or questions.

 



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