n: Compute the number of ranges in each group.
In plyranges: A fluent interface for manipulating GenomicRanges

This function should only be used within summarise(), mutate() and filter().

n()

n() will only be evaluated inside a function call, where it returns an integer.

ir <- as_iranges(
                 data.frame(start = 1:10,
                            width = 5,
                            name = c(rep("a", 5), rep("b", 3), rep("c", 2))
                            )
                )
by_names <- group_by(ir, name)
summarise(by_names, n = n())
mutate(by_names, n = n())
filter(by_names, n() >= 3)