QGIS-Atlas get feature with multiple values

Question

I am looking for an expression to get_feature with two values from two different fields.

At its core is the question: How can I transform a chain of values which define a point into a valid geometry expression? For example for Point B:

?? geometry ("obj_art" = 'Ansicht' and  "ptnr" = 'B')   ??

Kasper has given us the answer to the question how a geometry can be defined over several values. You can use the aggregate ( ) expression. On the last position (filter:=), an arbitrarily long chain of values or conditions can be placed. The expression is unfortunately not self explanatory, but there are plenty of examples.

aggregate(layer:=' ', aggregate:=' ', expression:= , 
filter:="prof_nr"= @atlas_pagename and "obj_art"='Ansicht' and "ptnr" ='B' and so on and so on  )

My Goal is to plot archaeological profiles via QGIS Atlas. Therefore I want to use Point A and Point B to filter page name. As coverage layer I have a point layer in which point A and B are located. Both points have the same value in field “prof_nr” so that is page name. Both points are defined by two other values from two different fields (Image 1).

My approach is to make_line out of both points, so that I always get only one Atlas feature per archaeological profile on which the map zooms in the middle. Both points can be easily called by CASE WHEN but with the expression I do not succeed in creating a line (Image 1)

CASE WHEN "obj_art" = 'Ansicht' and  "ptnr" = 'A' or  "obj_art" ='Ansicht' and  "ptnr" = 'B' THEN "prof_nr"  END

Therefore I select only point A for page name and moved the make_line to the extents of the map (Image2, 3)

x_min(  
bounds( 
    make_line(
        start_point(@atlas_geometry),geometry(
            get_feature('E_Point', 'ptnr','B')      
                                              )
             )
       )
   )

Here I can connect both points with make_line, but with get_feature I can only assign a value from one field but to define the point I need two values from two fields for each point.

Does anyone have a solution?

Answer 1

The Solution ist to override the x_Extents of the map!

For x_min I call point A

x_min(
aggregate (layer:='E_Point',aggregate:='collect',
expression:=bounds($geometry)
,filter:="prof_nr"= @atlas_pagename and "obj_art"='Ansicht' and "ptnr" ='A' )
    )

For x_max I call point B

x_max(
aggregate (layer:='E_Point',aggregate:='collect',
expression:=bounds($geometry)
,filter:="prof_nr"= @atlas_pagename and "obj_art"='Ansicht' and "ptnr" ='B' )
     )

Filter for pagename is to call Point A (or Point B, it doesn't matter)

CASE WHEN "obj_art" = 'Ansicht' and  "ptnr" = 'A' THEN   "prof_nr" END

That's it