Conditional value output in QGIS field calculator for array aggregation

Question

I have a three point across x with five repeating rows with this attributes:

[ 2, 1, 1 ]
[ 1, 2, 2 ]
[ 1, 1, 1 ]
[ 2, 2, 2 ]
[ 4, 4, 4 ]

I want to calculate a new field which aggregates the rows, currently I have: array_min(array_agg( "collumn", group_by:="row" ))

This will compute this result:

[ 2, 1, 1 ] -> 1
[ 2, 2, 2 ] -> 2
[ 1, 1, 1 ] -> 1
[ 2, 2, 2 ] -> 2
[ 4, 4, 4 ] -> 4

What I'm aiming to do next is to do a conditional where if the row aggregates is lower than the previous row aggregates, use that lower value instead of the computed value.

[ 2, 1, 1 ] -> 1: OK
[ 2, 2, 2 ] -> 2: OK
[ 1, 1, 1 ] -> 1: Lower than previous, use previous
[ 2, 2, 2 ] -> 2: OK
[ 4, 4, 4 ] -> 4: OK

I'm constrained on only using QGIS field calculator. Temporary field is allowed. What are my options?

Answer 1

Something like this:

if(
    array_min(array("a","b","c"))
    <
    array_min(
        array(
            attribute(get_feature_by_id(@layer,$id-1), 'a'),
            attribute(get_feature_by_id(@layer,$id-1), 'b'),
            attribute(get_feature_by_id(@layer,$id-1), 'c')
            )
        )
    ,
    array_min(
        array(
            attribute(get_feature_by_id(@layer,$id-1), 'a'),
            attribute(get_feature_by_id(@layer,$id-1), 'b'),
            attribute(get_feature_by_id(@layer,$id-1), 'c')
            )
        )
    ,
    array_min(array("a","b","c"))
    )

Note that depending on your exact requirements you may want to use get_feature() instead of get_feature_by_id(). In my example no gaps in the id's are allowed.