OpenEuphoria

Re: Mathematicians !! Percentile/Quartile function

• Posted by Pete Stoner <stoner.pete at gmail.com> Sep 07, 2005
• 587 views

Lucius L. Hilley III wrote:
> 
> <a
> href="http://www.vias.org/tmdatanaleng/cc_quartile.html">http://www.vias.org/tmdatanaleng/cc_quartile.html</a>
> 
> Depends on how you want to do it.
> I would think that the quartile would be sort of a median between medians
> but...
> It looks as though the above links definition differs slightly.
> It defines the median as the average of the 2 middle numbers if you have an
> even number of values.
> However, it defines the first and third quartile as a specific value that is
> in the list of values.
> 
> }}}
<eucode>
> --Warning: Code should be close enough to rounding for positive numbers.
> function positive_round(object x)
>   return floor(x+0.5)
> end function
> 
> --Warning: Code should be close enough to rounding for negative numbers.
> function negative_round(object x)
>   return floor(x-0.5)
> end function
> 
> function round(object x)
>   object px, nx
> 
>   px = x * (x > 0)
>   nx = x * (0 > x)
> 
>   return positvie_round(px) + negative_round(nx)
> end function
> 
> function quartile(sequence list)
>   integer n, q1_index, q2_index, q3_index
>   atom median
> 
>   n = length(list)
>   q1_index = round((n+1)/4) -- This could easily be optimized
>   q2_index = n/2
>   q3_index = round((n+1)*3/4) -- This could be optimized as well
>   
>   median = list[q2_index]
>   if (n = floor(n)) then -- if even(n) then
>     median += list[q2_index+1]
>     median /= 2
>   end if
> 
>   sequence {list[q1_index], median, list[q3_index]}
> end function
> 
> print(1, quartile({2,6,7,10,14,15}))
> puts(1, 10) -- new line
> machine_proc(26, 0) -- wait_key() cheat !!!
> <font color="#330033"></eucode>
{{{
</font>
> 
>   This code was proudly presented by:
>     Lucius L. Hilley III - Unkmar
> 

Nice try Lucius, but that gives 2, 8.5 and 10.. Correct median but 1st and 3rd
 quartiles are way off..

Regards Pete.