Hi,
I have a polygon layer and a line layer.
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.
I thought I use the field calculator and the aggregate function but I did not succeed.
What I have now is:
aggregate( layer:='line_layer', aggregate:= 'sum', _expression_:='length', filter:='measure=1')
which returns NULL
In the line layer there is an attribute 'length' that already holds the length of the element.
I only want the lines that have the attribute "measure=1".
Any help appreciated!
Regards,
Roland
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