Free and Open Source GIS Ramblings

Aggregate all the things! (QGIS expression edition)


In the past, aggregating field values was reserved to databases, virtual layers, or dedicated plugins, but since QGIS 2.16, there is a way to compute aggregates directly in QGIS expressions. This means that we can compute sums, means, counts, minimum and maximum values and more!

Here’s a quick tutorial to get you started:

Load the airports from the QGIS sample dataset. We’ll use the elevation values in the ELEV field for the following examples:

QGIS sample airport dataset – categorized by USE attribute

The most straightforward expressions are those that only have one parameter: the name of the field that should be aggregated, for example:


We can also add a second parameter: a group-by field, for example, to group by the airport usage type, we use:


To top it all off, we can add a third parameter: a filter expression, for example, to show only military airports, we use:


Last but not least, all this aggregating goodness also works across layers! For example, here is the Alaska layer labeled with the airport layer feature count:


If you are using relations, you can even go one step further and calculate aggregates on feature relations.