The Art of R Programming

Vector Element Names

The elements of a vector can optionally be given names. For example, say we have a 50-element vector showing the population of each state in the United States. We could name each element according to its state name, such as "Montana" and "New Jersey". This in turn might lead to naming points in plots, and so on.

We can assign or query vector element names via the names() function:

> x <- c(1,2,4)
> names(x)
NULL
> names(x) <- c("a","b","ab")
> names(x)
[1] "a"  "b"  "ab"
> x
 a  b ab
 1  2  4

We can remove the names from a vector by assigning NULL:

> names(x) <- NULL
> x
[1] 1 2 4

We can even reference elements of the vector by name:

> x <- c(1,2,4)
> names(x) <- c("a","b","ab")
> x["b"]
b
2