OpenEuphoria

Re: Mathematicians !! Percentile/Quartile function

• Posted by CChris <christian.cuvier at insee.fr> Sep 08, 2005
• 616 views

Pete Stoner wrote:
> 
> Pete Stoner wrote:
> > 
> > Pete Lomax wrote:
> > > 
> > > On Wed, 07 Sep 2005 09:45:41 -0700, Pete Stoner
> > > <guest at RapidEuphoria.com> wrote:
> > > 
> > > >i.e. for values of {2, 6, 7, 10, 14, 15, 16} the quartiles are 6.5, 10
> > > >and 14.5
> > > >but for a range of {2, 6, 7, 10, 14, 15} the correct quartiles seem to be
> > > >6.25, 8.5 & 13
> > > FWIW, (and strictly from observation only!) the first is (or might be)
> > >  (6+7)/2, 10, (14+15)/2, while ths second is (or might be)
> > > (2+6+7+10)/2, (7+10)/2, (10+14+15)/2
> > > 
> > > As I don't have either Excel or 123 to hand, I can't experiment more,
> > > but I wonder what happens with sets of longer numbers.
> > > 
> > 
> > I just tried it with a larger set..
> > {2,2,2,3,6,6,8,8,10,12,12,14,16,19,22,25,28,28,32,33}
> > results are Lucius - 3, 12, 22
> > Juergen and I got 6, 12, 23.5
> > 123 and Excel give 6, 12, 22.75
> > 
> > Regards Pete
> > 
> 
> and since the results seem to get closer with a larger sample...
> with
> {2,2,2,3,6,6,8,8,10,12,12,14,16,19,22,25,28,28,32,33,34,35,36,38,40,41,45,48,49,51,53,56,57,57,57,59,61,61,62,62}
> Lucius - 10, 33.5, 51
> Juergen and I got 12, 33.5, 52
> 123 and Excel give 12, 33.5, 51.5
> 
> Maybe I should run this as a competition! 
> 

include sort.e

function quartile(sequence data,integer whichOne)
-- matches what Excel returns

integer lowerObs
atom interPoint

data=sort(data)

if whichOne=0 then return data[1]   -- min
elsif whichOne=4 then return data[$]  -- max
elsif whichOne<0 or whichOne>4 then return 1/0  -- invalid
else
   interPoint=(3+length(data))/4
   lowerObs=floor(interPoint)
   interPoint-=lowerObs
   return (1-interPoint)*data[lowerObs]+interPoint*data[lowerObs+1]
end if
end function

HTH
define an ldata integer to use instead of $ under 2.4.

CChris