Brian Schott wrote:
> More recently I have been creating permutation vectors of a
> different sort using "permute" as in the following example inspired by one
> in the J vocabulary, called h.
>
> ]h =: (2 1; 0 1) C. i.4
> 1 2 0 3
>
> But h cannot be used in the "from" form h&{"1 to permute other vectors.
> Instead I have found that "amend" in (h})"1~ is effective.
>
> ]k=: 0 1 2 3,:4 5 6 7
> 0 1 2 3
> 4 5 6 7
> (h})"1~ k
> 2 0 1 3
> 6 4 5 7
Could you explain what you are getting at here? The permutation you are
using is not h but its inverse
hh=:2 0 1 3
and this behaves perfectly normally:
hh {"1 k
2 0 1 3
6 4 5 7
Amend works rather than select because of this inversion.
Best wishes,
John
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