You can use the length() function in R to calculate the length of vectors, lists, and other objects.
This function uses the following basic syntax:
- x: The name of the object to calculate length for
The following examples show how to use this function in different scenarios.
Example 1: Use length() with Vector
The following code shows how to use the length() function to calculate the number of elements in a vector:
#create vector my_vector <- c(2, 7, 6, 6, 9, 10, 14, 13, 4, 20, NA) #calculate length of vector length(my_vector)  11
We can see that the vector has 11 total elements.
Note that length() also counts NA values.
To exclude NA values when calculating the length of a vector, we can use the following syntax:
#create vector my_vector <- c(2, 7, 6, 6, 9, 10, 14, 13, 4, 20, NA) #calculate length of vector, excluding NA values sum(!is.na(my_vector))  10
We can see that the vector has 10 elements that are non-NA values.
Example 2: Use length() with List
The following code shows how to use the length() function to calculate the length of an entire list along with the length of a specific element in a list:
#create list my_list <- list(A=1:5, B=c('hey', 'hi'), C=c(3, 5, 7)) #calculate length of entire list length(my_list)  3 #calculate length of first element in list length(my_list[])  5
From the output we can see that the list has 3 total elements and we can see that the first element in the list has a length of 5.
Example 3: Use length() with Data Frame
If we use the length() function with a data frame in R, it will return the number of columns in the data frame:
#create data frame df <- data.frame(team=c('A', 'B', 'B', 'B', 'C', 'D'), points=c(10, 15, 29, 24, 30, 31)) #view data frame df team points 1 A 10 2 B 15 3 B 29 4 B 24 5 C 30 6 D 31 #calculate length of data frame (returns number of columns) length(df)  2
If we would like to calculate the number of rows instead, we can use the nrow() function:
#calculate number of rows in data frame nrow(df)  6
This tells us that there are 6 total rows in the data frame.
Example 4: Use length() with String
If we use the length() function with a string in R, it will typically just return a value of one:
#define string my_string <- "hey there" #calculate length of string length(my_string)  1
To actually count the number of characters in a string, we can use the nchar() function instead:
#define string my_string <- "hey there" #calculate total characters in string nchar(my_string)  9
This tells us that there are 9 total characters in the string, including spaces.
The following tutorials explain how to perform other common operations in R: