How about no parentheses.

h=: 13 :'|:i.~&> y'
   h i
0 0
1 0
2 2
0 0
1 4
2 2
2 6
2 2
1 2
2 6
   h
[: |: i.~&>

Linda

-----Original Message-----
From: [email protected] 
[mailto:[email protected]] On Behalf Of bill lam
Sent: Thursday, December 17, 2015 11:38 AM
To: 'Pascal Jasmin' via Programming
Subject: Re: [Jprogramming] nub and key of inverted table

Thanks. I can see your expression is
  |:@:>@(i.~L:0 ])
which gives the same x i. x as suggested by Roger.

Чт, 17 дек 2015, jprogramming написал(а):
> I have
> 
> 
> 
> nubi =. ({~ each"_ 1 ~.@|:@:>@((i."_ _1~) leaf~)) f.
> 
> 
> 
> keyi =. (i."_ _1~)@:(|:@:>@((i."_ _1~) leaf~))f.
> 
> 
> 
> still gives same unique indexes, just not contiguous.
> 
> (i."_ _1 ])@:(|:@:>@((i."_ _1 ]) leaf ])) i
> 0 1 2 0 4 2 6 2 8 6
> 
> 
> 
> ----- Original Message -----
> From: bill lam <[email protected]>
> To: jprogramming <[email protected]>
> Sent: Thursday, December 17, 2015 10:21 AM
> Subject: [Jprogramming] nub and key of inverted table
> 
> I want an effecient method of finding nub and key of a inverted table 
> (rank-1 box array with equal number of items in each cells).  eg.
> 
>    ]i=. (,.0 2 1 0 2 1 1 1 2 1);10 2$'aaaabaaaabbabbbababb'
> +-+--+
> |0|aa|
> |2|aa|
> |1|ba|
> |0|aa|
> |2|ab|
> |1|ba|
> |1|bb|
> |1|ba|
> |2|ba|
> |1|bb|
> +-+--+
> 
> NB. nub of i
>    ifa ~. a=. afi i
> +-+--+
> |0|aa|
> |2|aa|
> |1|ba|
> |2|ab|
> |1|bb|
> |2|ba|
> +-+--+
> 
> NB. key of i
>    a i.~ ~.a
> 0 1 2 0 3 2 4 2 5 4
> 
> NB. definition of afi and ifa
>    afi
> |:@:(<"_1@>)
>    ifa
> <@(>"1)@|:
> 
> Although nub and key can be found using afi/ifa, it involves a lot of 
> box, I worry the time and space efficency when the table is large.  
> Can anyone suggest other ways to do it.
> 
> --
> regards,
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