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R Lists
Lists
List R can contain many different types of data within it. List a single and flexible data collection.
To create a list, use the list() function:
Example
thislist <- list("apple", "banana", "cherry")
# Print the list
thislist
Access Lists
You can access the list items by referring to its reference number, inside brackets. The first item has point 1, the second item has point 2, and so on:
Example
thislist[1]
Change Item Value
To change the value of an item, see the reference number:
Example
thislist[1] <- "blackcurrant"
# Print the updated list
thislist
List Length
To find out how many items the list has, use the length() function:
Example
length(thislist)
Check if Item Exists
To find out if something is listed, use %in% operator:
Example
"apple" %in% thislist
Add List Items
To add an item to the end of the list, use the append() function:
Example
Add "orange" to the list:
append(thislist, "orange")
To add an item to the right of a specific index, add "after = index number" to the append() function:
Example
Add "orange" to the list after "banana"(index 2):
append(thislist, "orange", after = 2)
Remove List Items
You can also delete list items. The following example creates a new, updated list without the "apple" item:
Example
Remove "apple" from the list:
newlist <- thislist[-1]
# Print the new list
newlist
Range of Indexes
You can specify a range of indicators by specifying where to start and where to end the range, using : operator:
Example
Return the second, third, fourth and fifth item:
(thislist)[2:5]
Note: Search will start in index 2 (included) and end in index 5 (included).
Remember that the first item has index 1.
Loop Through a List
You can access the list items by using the for loop:
Example
for (x in thislist) {
print(x)
}
Join Two Lists
There are several ways to join, or merge, two or more columns in R.
The most common method is to use the c() function, which combines two elements together:
Example
list2 <- list(1,2,3)
list3 <- c(list1,list2)
list3