On Sun, Nov 4, 2012 at 3:25 PM, Michal D. <michal.dobrog...@gmail.com> wrote:
> (0 1 4).  I follow the argument for (arcs=: $ #: I.@) but my J is slow.  We
> would have to be able to select an or of equals for example select from first
> column where the value is 0 or 1 or 4.

Here's select the rows of Y where number in the first column is contained in X:

   X ((e.~ {."1) # ]) Y

For example:

   sel0=: (e.~ {."1) # ]
   7 21 35 sel0 i. 7 7

FYI,

-- 
Raul
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