A.6 Summarising Ranges
The summarise function will return a DataFrame because the information
required to return a Ranges object is lost. It is often most useful to use
summarise() in combination with the group_by() family of functions.
#> DataFrame with 2 rows and 2 columns
#> query gc
#> <integer> <numeric>
#> 1 1 0.675555
#> 2 2 0.635795