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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?

  • @Aaron, thank you for the suggestion, do you know how using the spatial join I can count the occurrences in the polygon, all the spatial join tools i've looked at offer stats like mean, stdev, etc. but not CountOf. – hselbie Nov 24 '15 at 2:25
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Your guess is correct - use 'Count Unique Points in Polygon' in the processing toolbox, using "car_id" as the "Class field".

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