Count unique features of points in polygon

I have a series of points with various fields in the attribute table such as car_id, time etc.,

I've created a hexagon vector grid, I want to count how many unique car_id's occur in one of the hexagon polygons.

Essentially a step further than points in polygon, if there are multiple points in a polygon where car_id = 25, the car_id = 25 would be counted once. The car_id count for a polygon using the sample data below would be 4

car_id = 25 car_id = 25 car_id = 25 car_id = 22 car_id = 22 car_id = 23 car_id = 24

My question is what is the most appropriate QGIS tool to achieve this? Would it be Count Unique Points in Polygon, in the processing toolbox?

Your guess is correct - use 'Count Unique Points in Polygon' in the processing toolbox, using "car_id" as the "Class field".

Watch the video: QGIS - Statist - Display Statistics such as count, sum, min, max, etc (October 2021).