A bigger problem might be the slight upward bias in this algo.  It's
exacerbated if you have a lot of halves in your data:

   rr=. -: 100?@$100
   usus rr            NB. usus -> usual stats: Min, max, mean, SD
0 49.5 27.63 14.7935
   usus round rr      NB. Higher mean: significant?
0 50 27.9 14.7802

   mean&> (round;]) -: 100?@$100
22.28 21.975
   -/mean&> (round;]) -: 100?@$100
0.275
   -/mean&> (round;]) -: 100?@$100
0.225

   $100 ([: -: ?@$)&.>100$100
100

   usus ([: -/ [: mean&> round ; ]) &> 100 ([: -: ?@$)&.>1e6$100
0.13 0.365 0.250008 0.0249975
   NB. Could be significant...


On Tue, Jan 22, 2013 at 12:08 PM, Raul Miller <[email protected]> wrote:

> I don't think that that definition of round can be tacit and use under.
>
> A tacit implementation might be:
>    1&$: : ([ * <.@+~&1r2@%~)
>
> Note also: this is a verb, not an adverb. In this definition, 1 is the
> default value for x, not a control argument for :
>
> FYI,
>
> --
> Raul
>
> On Tue, Jan 22, 2013 at 11:55 AM, David Ward Lambert
> <[email protected]> wrote:
> >    round =: 1&$: : (dyad def '<.@:(1r2+])&.:(%&x) y')
> >    assert 1 -: round 1.2
> >    assert 1.25 -: 0.25 round 1.2
> >
> >    Round =: adverb def '<.@:(1r2+])&.:(%&m) y'
> >
> > Is there a tacit definition of round using under?
> > What is the tacit definition of adverb Round?
> > Thanks, Dave.
> >
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>



-- 
Devon McCormick, CFA
^me^ at acm.
org is my
preferred e-mail
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