lttb_8.sql

largesttriangle(grp,p) as (

  select
    wga.grp,
    ((0,0),(wga.x,wga.y),(0,0),0.0)::triangle_t
  from withgrpavg wga
  where grp = 1
  
  union all
  
  select distinct
    wga.grp,
    (largest_triangle(
      (ltt.p).p2, -- the selected point of the previous bucket
      (wga.x,wga.y), -- current bucket
      (wga.xavg3,wga.yavg3)::triangle_t -- average of next bucket
    ) over (partition by wga.grp)
  from withgrpavg wga join largesttriangle ltt on wga.grp=ltt.grp+1
  where wga.grp > 1
)