R function: length

Counting the elements in a vector

If applied to a vector, length() counts its elements:

length(42:100)
# [1] 59

length("foo")
# [1] 1

length("")
# [1] 1

length(c())
# [1] 0

length(c("foo"))
# [1] 1

length(c("foo", "bar"))
# [1] 2

If applied to a data frame, length() returns the number its columns.

In order to determine the number of observations of a data frame, nrow() can be used.