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# Set up initial 4x4 matrix with some arbitrary data
pdl> p $b = pdl (10..25)->reshape(4,4);
...
pdl> p $b->indexND($pos + $xfrm, 'truncate');
[20 17 0 25]
# $b->range($pos + $xfrm, 1, 'truncate') gives similar results

pdl> p $indicies = $b->indexND($pos + $xfrm, 'truncate')->which($b % 2
+);
# Returns: empty
#
...
#  [3 3]   # 25
# ]
# N.b. [2 2] would be omitted (value = 20, even), as would [4 2] (inde
+x out of bounds)