Attaching package: 'dplyr'
The following objects are masked from 'package:stats':
    filter, lag
The following objects are masked from 'package:base':
    intersect, setdiff, setequal, union
Attaching package: 'data.table'
The following objects are masked from 'package:dplyr':
    between, first, last
[1] 78974    67
[1] TRUE
[1] TRUE
[1] TRUE
[1] 2206675       9
`summarise()` has grouped output by 'age'. You can override using the `.groups`
argument.
`summarise()` has grouped output by 'age'. You can override using the `.groups`
argument.