Using aggregate function in QGIS graphical modeler?

Question

I'm looking to create five fields of grouped means within 33 shapefiles. I'm using the Graphical Modeler to save me using the Field Calculator 5 x 33 times.

The new fields are the means of the traffic volumes ("AADT") of five modes, grouped by road types ("DESC_TERM") in the shapefiles. These functions work when calculating 'manually':

mean( "AADTallc_1" , "DESC_TERM" , "AADTallc_1" != 0.0)
mean( "AADTalllgv" , "DESC_TERM" , "AADTalllgv" != 0.0)
mean( "AADTTaxi" , "DESC_TERM" , "AADTTaxi" != 0.0)
mean( "AADTMotorc" , "DESC_TERM" , "AADTMotorc" != 0.0)
mean( "AADTLtBus" , "DESC_TERM" , "AADTLtBus" != 0.0)

I've created this flow on Graphical Modeler:

Model flow

Where for LGVs (where the model fails);

LGVs input

With the failure message "An error occurred while evaluating the calculation string: Cannot use aggregate function in this context":

Failure message

What could be going wrong?

I tried changing the parameters, but nothing seems to work.

• underdark: Did you find any documentation that says that this should work? I'm not sure it's possible to calculate aggregates like this.
• MoMiJi: Not in particular, I was following this video for the basic structure: youtube.com/watch?v=XyPW8mzssZE It works for the first procedure (road_car) but not the second
• underdark: What does road_car do? Please include a screenshot
• MoMiJi: road_car produces the same output as the LGVs step but for cars, using mean( "AADTallc_1" , "DESC_TERM" , "AADTallc_1" != 0.0) under Formula.
• jlSta: Same problem for me with 2.18.16. When i use refactor fields with 'aggregate' function from processing toolbox , it works. But not in model... Formula is concatenate( "vote" , "id_ws" , "user" NOT LIKE 'zp%' AND "user" NOT LIKE 'zp%')

Answer 1

The issue looks solved.

You should update since 2.18.17 is released or try to install nightly from osgeo4w with the advanced install.

https://issues.qgis.org/issues/17300