There is also:
a =: i.3 4
{i. each $ a
+---+---+---+---+
|0 0|0 1|0 2|0 3|
+---+---+---+---+
|1 0|1 1|1 2|1 3|
+---+---+---+---+
|2 0|2 1|2 2|2 3|
+---+---+---+---+
Ben
________________________________________
From: Programming [[email protected]] on behalf of Skip
Cave [[email protected]]
Sent: Wednesday, January 11, 2017 00:05
To: [email protected]
Subject: [Jprogramming] Indices of a matrix
Given a 3x4 matrix:
a =. i. 3 4
a
0 1 2 3
4 5 6 7
8 9 10 11
I can get the horizontal indices:
4|a
0 1 2 3
0 1 2 3
0 1 2 3
How do I get the vertical indices?
3?a NB. The question-mark represents the unknown verb
0 0 0 0
1 1 1 1
2 2 2 2
Ultimately, I want to design a verb bix, that will take a list of
dimensions of any length, and generate boxed indices of the resulting
array. The number of integers in each box will be the same as the rank of
the array:
bix 10
┌─┬─┬─┬─┬─┬─┬─┬─┬─┬─┐
│0│1│2│3│4│5│6│7│8│9│
└─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘
bix 3 4
┌───┬───┬───┬───┐
│0 0│0 1│0 2│0 3│
├───┼───┼───┼───┤
│1 0│1 1│1 2│1 3│
├───┼───┼───┼───┤
│2 0│2 1│2 2│2 3│
└───┴───┴───┴───┘
bix 2 3 4
┌─────┬─────┬─────┬─────┐
│0 0 0│0 0 1│0 0 2│0 0 3│
├─────┼─────┼─────┼─────┤
│0 1 0│0 1 1│0 1 2│0 1 3│
├─────┼─────┼─────┼─────┤
│0 2 0│0 2 1│0 2 2│0 2 3│
└─────┴─────┴─────┴─────┘
┌─────┬─────┬─────┬─────┐
│1 0 0│1 0 1│1 0 2│1 0 3│
├─────┼─────┼─────┼─────┤
│1 1 0│1 1 1│1 1 2│1 1 3│
├─────┼─────┼─────┼─────┤
│1 2 0│1 2 1│1 2 2│1 2 3│
└─────┴─────┴─────┴─────┘
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