How to reshape and ravel arrays

Reshape a vector into a matrix

      3 4 ⍴ ⍳12                 ⍝ 3 rows, 4 columns

Create an array filled with a constant

      5 5 ⍴ 0                   ⍝ 5×5 matrix of zeros
      2 3 ⍴ 1                   ⍝ 2×3 matrix of ones

Flatten any array to a vector

      , 3 4 ⍴ ⍳12               ⍝ ravel to a 12-element vector

Reshape with recycling

      3 3 ⍴ 1 0                 ⍝ alternating 1s and 0s