Sort polygons from north to south in QGIS using 'graphical modeler'?

Question

I'm building a model in 'graphical modeler' in QGIS 2.2.

I want my model to clip a polygon layer and give the polygons coordinates so that I could sort them geographically from north to south. After sorting them, I want to add a number to each polygon to be able to save the sorted order.

I have, with some help from this forum, been able to add coordinates to the polygons using the modeler. So far, everything is good.

My next step would be to get the polygons sorted from north to south. I have done these last few steps manually, sorting the polygons in the attribute table, added a column with "sorting number", and then saving the sorted order using MMQGIS - 'Modify' - 'Sort'.

Is it at all possible to do something similar inside the graphical modeler? I'm going to do this mulitple times, so it would be a real timesaver to get as many steps as possible inside the modeler.

Answer 1

One simple process and available in Model builder is:

1. Use FIeld calculator

2. Formula:

   distance($geometry, geom_from_wkt('Point (149451.55066836 189178.84799332)')) 
   

   where the point is above your polygon in North direction. You can stop now or continue point 3.

3. In spreadsheet, do a semi automatic classification by creationg groups. Then do one first sort on this group then the second on distance and finally make an incremental numbering. Then join the spreadsheet.