I want to create a dataset containing information about civilian deaths in areas near UNPKOs. Therefore, I use the Geo-PKO dataset, which geocodes UN peacekeeping missions, and the UCDP-ged dataset, which geocodes violent conflict. I created buffer zones for each mission and want to know how many civilians died within that buffer zone. The problem is that I need to remove all civilian deaths that happened before the installation of a mission.
Both datasets have a year variable. So I want to remove any observation from a buffer zone if the year variable of the buffer zone is bigger than the year variable of the violent incident.