One common error you may encounter in R is:
$ operator is invalid for atomic vectors
This error occurs when you attempt to access an element of an atomic vector using the $ operator.
An “atomic vector” is any one-dimensional data object created by using the c() or vector() functions in R.
Unfortunately, the $ cannot be used to access elements in atomic vectors. Instead, you must use double brackets [[]] or the getElement() function.
This tutorial shares examples of how to deal with this error in practice.
How to Reproduce the Error Message
Suppose we attempt to use the $ operator to access an element in the following vector in R:
#define vector x #provide names names(x) #display vector x a b c d e 1 3 7 6 2 #attempt to access value in 'e' x$e Error in x$e : $ operator is invalid for atomic vectors
We receive an error because it’s not valid to use the $ operator to access elements in atomic vectors. We can also verify that our vector is indeed atomic:
#check if vector is atomic
is.atomic(x)
[1] TRUE
Method #1: Access Elements Using Double Brackets
One way to access elements by name in a vector is to use the [[]] notation:
#define vector
x #provide names
names(x)
#access value for 'e'
x[['e']]
[1] 2 Method #2: Access Elements Using getElement()
Another way to access elements by name in a vector is to use the getElement() notation:
#define vector
x #provide names
names(x)
#access value for 'e'
getElement(x, 'e')
[1] 2 Method #3 Convert Vector to Data Frame & Use $ Operator
Yet another way to access elements by name in a vector is to first convert the vector to a data frame, then use the $ operator to access the value:
#define vector x #provide names names(x) #convert vector to data frame data_x data.frame(t(x)) #display data frame data_x a b c d e 1 1 3 7 6 2 #access value for 'e' data_x$e [1] 2
Additional Resources
The following tutorials explain how to troubleshoot other common errors in R:
How to Fix in R: names do not match previous names
How to Fix in R: NAs Introduced by Coercion
How to Fix in R: Subscript out of bounds
How to Fix in R: contrasts can be applied only to factors with 2 or more levels