From (⌷)

Syntax

i ⌷ Y

Selects major cells (first-axis slices) of Y at the indices given by i.

Result shape

(⍴i) , 1↓⍴Y

When i is a scalar, the result has the shape of a single major cell (1↓⍴Y).

Examples

Vector selection:

      2 ⌷ 10 20 30 40 50
20
      2 4 ⌷ 10 20 30 40 50
20 40

Matrix row selection:

      2 ⌷ 3 4⍴⍳12
5 6 7 8
      1 3 ⌷ 3 4⍴⍳12
1 2  3  4
9 10 11 12

Index origin

Respects ⎕IO. With ⎕IO←0, the first major cell has index 0.

      ⎕IO←0
      0 ⌷ 10 20 30
10

Errors

• RANK ERROR if Y is a scalar (scalars have no major cells).
• INDEX ERROR if any index is out of range.

See also

• Bracket Indexing -- V[i], M[r;c]