Calculating mean value of polygons based on attributes of point layer in QGIS

Question

I am working with QGIS to compute the annual burned area of my study area in Chile. I have two different layers.

• One polygon layer which is a 1km x 1km grid of my study area. The only information this layer contains is a unique "id" for every grid cell.
• The second layer is a point layer of fires. It contains information about the size, direction and duration of the fire. Every point is one fire. Multiple points (fires) can lie within a grid cell.

I now want to compute the average size of fires in each grid cell. How can that be accomplished?

Answer 1

This is an example trying to mimic your situation. Please modify layernames and field names according to your project.

Above figure shows two layers: Fire point layer with size field, and Grid layer with id field only.

Start Field Calculator on the Grid layer, and give this expression:

array_mean(overlay_contains('Fire', expression:= "size"))

It will return averaged fire size. (It returns null where you do not have any fire).