Models — Row at a Time

dotr  ← {↑ (↓⍺) ⍺⍺{⍺⍺⌿⍺ ⍵⍵[0] ⍵}⍵⍵¨ ⊂⍵}
dotr1 ← {↑ (↓⍺) ⍺⍺⌿at(⍵⍵[0])¨ ⊂⍵}