<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>Hi,</div>
<div>I have a polygon layer and a line layer.</div>
<div>I would like to update a field in the polygon layer with the length of the lines in each polygon that have a certain value in an attribute.</div>
<div>I thought I use the field calculator and the aggregate function but I did not succeed.</div>
<div>What I have now is:</div>
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<div>aggregate( layer:='line_layer', aggregate:= 'sum', expression:='length', filter:='measure=1')</div>
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<div>which returns NULL</div>
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<div>In the line layer there is an attribute 'length' that already holds the length of the element.</div>
<div>I only want the lines that have the attribute "measure=1".</div>
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<div>Any help appreciated!</div>
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<div>Regards,</div>
<div>Roland</div>
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