To add or append an element to the list in R use the append() function. This function takes 3 parameters input list, the string or list you wanted to append, and position.
The list.append() function from the rlist package can also append one list with another in R. In this article, I will explain how to append/add an element to a list by using the R base append() function and list.append() function from the list package with multiple examples.
Related: You can also add an element to the list using a loop in r.
1. Quick Examples of Adding Elements to List
Following are quick examples of adding or appending elements to the list in R.
# Quick examples of appending element to list
# Example 1: Using R base append()
li = list('java','python')
li2 <- append(li,'r')
print(li2)
# Example 2: Add element to list at specified position
li = list('java','python')
li2 <- append(li,'r',after=1)
print(li2)
# Example 3: Using list.append()
library('rlist')
li2 <- list.append(li,'r')
print(li2)
# Example 4: Named List
library('rlist')
li = list(id=11,name='python')
li2 <- list.append(li,pages=34)
print(li2)
# Example 5: Append list with another list
li = list('java','python')
li2 = list('r','php')
li3 <- append(li,li2)
print(li3)
2. R Base append() Syntax
Following is the syntax of the R base append() function
# Syntax of append()
append(x, values, after = length(x))
Parameters
x– Input listvalues– string, list or vector.after– Position to add. Optional. When not specified the element is added at the end of the list.
3. Append Element to List
You can use the append() function to add an element to the existing list in R. If you do not specify the position(in which we want to specify the position of an element) by default, it adds an element at the end of the list. The following example adds an element r to the list.
# Add element to list
li = list('java','python')
print(li)
li2 <- append(li,'r')
print(li2)
Yields below output. Note that we have added the item r to the list.
4. Add Element to List at Specified Position
You can use after parameter to specify the position where you want to add the element. The following example adds elements after the first position.
# Add element to list at specified position
li = list('java','python')
li2 <- append(li,'r',after=1)
print(li2)
Yields below output.
5. Add Multiple Elements to List
Package rlist provides a list.append() function to add multiple elements to the list in R. In order to use this function first, you need to install R package by using install.packages("rlist") and load it using the library("rlist").
# Add multiple elements to list
library('rlist')
li2 <- list.append(li,'r','50')
print(li2)
Yields below output.
# Output
[[1]]
[1] "java"
[[2]]
[1] "python"
[[3]]
[1] "r"
[[4]]
[1] "50"
Using this function we can also append elements to the named list.
# Named List
library('rlist')
li = list(id=11,name='python')
li2 <- list.append(li,pages=34)
print(li2)
6. Append the List with Another List
To append one list with another list pass both lists to the append() function, this adds a second list to the end of the first list and returns a single list.
# Append list with another list
li = list('java','python')
li2 = list('r','php')
li3 <- append(li,li2)
print(li3)
# Output:
# [[1]]
# [1] "java"
# [[2]]
# [1] "python"
# [[3]]
# [1] "r"
# [[4]]
# [1] "php"
7. Using c() to Append List
If you are unaware that c() is a combined function used to merge the list, vector etc.. The following example uses c() to append two lists.
# using c()
li3 = c(li,li2)
print(li3)
Yields the same as the above output.
Frequently Asked Questions of Append Element to List in R
You can use the c() function to concatenate or append elements to a list. For example, append_list <- c(my_list1, new_element)
rlist package provides a list.append() function to append multiple elements to the list in R. For example, library('rlist') my_list <- list.append(my_list1,'new_element1','new_element2')
Using the R base append() function with the after parameter to insert an element at a specific position. For example, my_list <- append(my_list1, new_element, after = 2)
To append a list to an existing list you can use the R base function. It appends the new list at the end of the existing list. For example, my_list <- append(my_list1, my_list2)
Conclusion
In this article, you have learned how to add or append an element to the list by using R base append(), list.append() from the rlist package. You can find the complete example from this article at Github R Programming Examples Project.
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