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From venkatesha murthy <venkateshamurth...@gmail.com>
Subject [MATH-1120] Needed opinion about support on variations in percentile calculation
Date Wed, 21 May 2014 19:18:22 GMT
Hi All,

The existing Percentile class calculates the percentile based on the
quantile position of the array fixed as
p * (N+1)/100 for a pth Percentile on an Array of size N. However if we
were to add these numbers in MS Excel
to calculate the percentile it provides a different result and closely
resembeles the formula [p*(N-1)/100]+1.

Its imperative at times to match the computations to a standard spreadsheet
calculations or to a standard tool;
which is why i request for allowing the quantile position to be customized.
Infact even the kth selection used
can also be refactored as a strategy(than as a private methods) as a
further step.

So if atleast the Percentile class were to allow the quantile position to
be customized in the sub classes; then
the end user may be helped in providing the formula of their choice.

The most minimal change i am proposing here is to just make the quantile
position setting as a protected method and i have attached a possible patch
in [MATH-1120] <https://issues.apache.org/jira/browse/MATH-1120>.

Request all to opinionate on this

thanks
venkat

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