QGIS spatial filtering expressions

Question

Using QGIS 3.4

I have a set of points and I am using the atlas tool to generate reports for each point.

I'm looking for a way to only create reports for points that intersect a polygon.

These polygons change all the time, so im looking for a more on the fly way to filter these points, rather than the traditional select and save as a new layer.

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In the atlas tools I see there is a "filter with" option and it gives you the ability to write an expression.

How can I create an expression/function to do the filter.

Answer 1

To filter the atlas features based on intersection with a single polygon, use this expression in the atlas filter, with substitutions as explained below:

 intersects( $geometry, geometry(get_feature('polygon_layer','attribute','value')))

• substitute the name of your polygon layer for 'polygon_layer'
• substitute the name of an attribute in your polygon layer for 'attribute'
• substitute the value of that attribute for the appropriate polygon for 'value'

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To filter the atlas features based on intersection with multiple polygons, use this expression in the atlas filter, with substitutions as explained above:

intersects( $geometry , aggregate( 'polygon_layer', 'collect', $geometry))