↑ — First / Take↑Y returns the first major item, like 1⊃Y. On an enclosure it returns the contained value. An empty leading axis gives a cell of fill.
↑(1 2⋄ 3 4 5) ⍝ 1 2
↑2 3⍴⍳6 ⍝ 1 2 3
↑⊂7 ⍝ 7
↑0 3⍴0 ⍝ 0 0 0
N↑Y takes leading items; negative N takes from the end. Overtake inserts fill.
4↑1 2 ⍝ 1 2 0 0
¯4↑1 2 ⍝ 0 0 1 2
Vector counts apply to successive leading axes. [K] selects axes.
1 2↑2 3⍴⍳6 ⍝ 1 2⍴1 2