: — Unkey / Keyed

Function. Ranks: ∞ monadic, 1 ∞ dyadic

:Y removes axis keys. K:Y labels leading axes. K:⍠A Y labels the axes A. A bracket list with any key:value item is one keyed vector. The list’s other items are entries without keys. See axis keys.

:"aa" "bb":1 2    ⍝ 1 2
"bb"⊃"aa" "bb":1 2 ⍝ 2
["aa":1 "bb":2]≡"aa" "bb":1 2 ⍝ $t

In K, a position’s own number leaves that position without a key. Axis names are the keys of the shape. N:⍴M ⍴ M renames the axes. See shape.

"aa" 1:10 20        ⍝ ["aa":10 20]
M←["city":2 "month":3]⍴⍳6
⍴M⍴⍨:⍴M            ⍝ [2 3]ₓ

A keyed K supplies axis names and position keys together.

axes←["city":"NY" "LA";"month":"Jan" "Feb" "Mar"]
M←axes:[1 2 3⋄4 5 6]
"LA" "Feb"⌷M       ⍝ 5

Inverse

K:⁻¹Y removes the keys K from Y, which must have exactly those keys.

"a" "b":⁻¹["a":1;"b":2]   ⍝ 1 2