Models — Row by Column

dotc    ← {↑ (↓⍺) ∘.(⍺⍺{⍺⍺/⍺ ⍵⍵ ⍵}⍵⍵) ↓(¯1⌽⍳⍴⍴⍵)⍉⍵}
dotc1   ← {↑ (↓⍺) ∘.(⍺⍺{⍺⍺/⍺ ⍵⍵ ⍵}⍵⍵) ↓flip ⍵}
dotc2   ← {↑ (↓⍺) ∘.(⍺⍺/at ⍵⍵) ↓flip ⍵}
dotc3   ← {↑ ⍺ ∘.(⍺⍺/at ⍵⍵)compose↓ flip ⍵}
dotc4   ← {⍺ ∘.(⍺⍺/at ⍵⍵)under↓ flip ⍵}   ⍝ nonce error
dotc5   ← {⍺ ∘.(⍺⍺/at ⍵⍵)under↓∘flip ⍵}   ⍝ nonce error

flip    ← {(¯1⌽⍳⍴⍴⍵)⍉⍵}
at      ← {⍺⍺(⍺ ⍵⍵ ⍵)}
compose ← {(⍵⍵ ⍺)⍺⍺(⍵⍵ ⍵)}
under   ← {(⍵⍵⍣¯1)(⍵⍵ ⍺)⍺⍺(⍵⍵ ⍵)}