I'm just getting started with QGIS. I have a layer of points with a specific value. How do I sum up the point values in a designated polygon?
You can also use field calculator with an expression such as:
points is the name of your point layer and
vals the fieldname containing the values. Apply this in the attribute table of your polygon layer via fieldcalculator.
Make sure both layers are in the same CRS as mentioned by @Babel.
To make this update automatically everytime you modify the polygon, you can add it as a virtual field. Simply check the box for that in fieldcalculator:
But note this attribute will only be available in your QGIS project. It is not stored permanently in your datasource!
array_sum (overlay_contains ('point_layer', "value"))
point_layer with the point layer's name and
value with the field name of the attribute that contains the value you want to sum up.