Statistics function incorrectly computing median

[Ben Abbott]

On Jan 26, 2008, at 6:39 AM, Miguel Garcia-Blanco wrote:

> My tests (using 40 samples with 6 observations ~N(0,100)) indicate
> everything seems to be okay, except quantile.m with METHOD = 3: For  
> six
> observations, the 3rd quartile should be the 4th order statistic.  
> Currently
> returns the 5th order statistic.
>
> -Miguel

I struggled quite a bit with #3. To be honest, I had little hope it  
was working properly. The part below was added to obtain agreement  
with R in several cases.

--------------------------------------------
----- from __quantile__.m, lines 92:96 -----
--------------------------------------------
   if (x(k(q)) <= 0.5)
     inv(k(q)) = v(find(dx == min(dx), 1, "first"));
   else
     inv(k(q)) = v(find(dx == min(dx), 1, "last"));
   endif
--------------------------------------------

I'm skeptical that part should be there. Any idea on what the proper  
algorithm for #3 might look like?

Ben
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