Using group_by Instead of Splits

TL;DR It is relatively easy to use dplyr::group_by and summarise to find items that you might want to keep or remove based on a part_of the item or group in question. I used to use split and iterate, but group_by is much easier. Motivation I have some relatively large sets of data that fall naturally into groups of items. Often, I find that I want to remove a group that contains either any of or all of particular items.