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I am trying to use the 'intersects' function within an 'if' condition. If a polygon in Layer A intersects a polygon in layer B, then the cell should display 'YES', otherwise 'No'.

However, I don't know how to properly call the Layer B in the field calculator. The expression I am working on looks like this :

if(intersects( $geometry,geometry('LayerB') ),"YES","NO")

Does anyone know how to put it correctly?

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    For one thing, the intersects command will return a true/false response without the if statement, so you can drop that part. More importantly, though, the intersects command requires that you have a specific geometry to test against. If you just want to check if it intersects ANY polygon in the second layer, you're going to need to do something a little more involved. Suggestion: use the Select by location tool to specify cross-layer intersections, then just create the new field and update selected features only.
    – jcarlson
    Commented Jun 12, 2018 at 15:03
  • I thought about 'Select By Location', but I wanted to use the graphical modeler and didn't know if it would work. Thank you !
    – Andare
    Commented Jun 12, 2018 at 15:22

2 Answers 2

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The correct syntax for your expression is 

    IF (aggregate(layer:='Layer B', aggregate:= 'count', expression:= $id, 
       filter:=intersects($geometry, geometry(@parent))), 
       concat ('yes'), concat('no'))

This is the result: enter image description here

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Using refFunctions :

if( intersecting_geom_count('LayerB') > 0, 'YES', 'NO' )

(Sorry it is not QGIS3.0 specific, not using intersects function...)

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