Index Element of List in R (3 Examples)
This tutorial shows how to return certain list elements using indices in the R programming language.
Table of contents:
Let’s dive into it!
Creation of Example Data
The following data will be used as basement for this R tutorial:
my_list <- list(1:5, # Create example list data.frame(x1 = 9:5, x2 = letters[1:5]), list(1:3, letters[8:6])) my_list # Print example list # [] #  1 2 3 4 5 # # [] # x1 x2 # 1 9 a # 2 8 b # 3 7 c # 4 6 d # 5 5 e # # [] # [][] #  1 2 3 # # [][] #  "h" "g" "f" # #
As you can see based on the previous output of the RStudio console, our example data is a list with three list items.
The first element of our list is a numeric vector, the second element is a data frame, and the third element is a nested list.
Example 1: Select Entire List Element
In Example 1, I’ll illustrate how to get an entire list element using double square brackets (i.e. “[]”).
The following R code returns the second element of our list, i.e. the data frame shown in Table 1:
my_list[] # Subset entire list element
Example 2: Select Sub-Element of List
In Example 2, I’ll illustrate how to return an element contained in a sub-element of our list.
The following R code extracts the value in the third row and second column of the data frame stored as second list element:
my_list[][3, 2] # Subset sub-element of list element #  "c"
Example 3: Select Nested List
This example shows how to extract values from a nested list in R.
Have a look at the following R code:
my_list[][] # Subset sub_list in list #  "h" "g" "f"
The first double brackets extract the third list element and the second double brackets extract the second list element of the nested list.
Video, Further Resources & Summary
Have a look at the following video which I have published on my YouTube channel. In the video, I illustrate the R code of this tutorial:
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Furthermore, you may want to read some of the other tutorials of my website.
- Get Second Sub Entry of Every List Element
- Append to List in Loop
- Test If List Element Exists
- Remove Element from List in R
- The R Programming Language
To summarize: At this point you should know how to extract a list element based on an index in the R programming language. In case you have additional comments or questions, don’t hesitate to let me know in the comments section.
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