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Richard Brunauer edited comment on MATH1347 at 3/21/16 12:02 PM:

No, I can’t provide a junit test. The mistake is in Javadoc and not in Java code. The results
are, for my opinion, correct.
I guess that the explanation is correct but the equation does not represent the explanation’s
semantics. Explanation and expression are semantically not equal!
Explaination in Percentile for the default/legacy case: “Else let lower be the element in
position floor(pos) in the array and let upper be the next element in the array. Return lower
+ d * (upper  lower)”
Equation in Percentile.EstimationType: x[ceil(h  1/2)]
I would expect the same equation for variable “estimate” as in R_6. Furthermore, the Percentile.EstimationType
“R_6” and “LAGACY” is almost a code copy (compare method index()).Is this intended?
To see the mistake:
https://commons.apache.org/proper/commonsmath/apidocs/org/apache/commons/math3/stat/descriptive/rank/Percentile.EstimationType.html
section: Enum Constant Detail
enum: LEGACY
was (Author: richard.brunauer@salzburgresearch.at):
No, I can’t provide a junit test. The mistake is in Javadoc and not in Java code. The results
are, for my opinion, correct.
I guess that the explanation is correct but the equation does not represent the explanation’s
semantics. Explanation and expression are semantically not equal!
Explaination in Percentile for the default/legacy case: “Else let lower be the element in
position floor(pos) in the array and let upper be the next element in the array. Return lower
+ d * (upper  lower)”
Equation in Percentile.EstimationType: x[ceil(h  1/2)]
I would expect the same equation for variable “estimate” as in R_6. Furthermore, the Percentile.EstimationType
“R_6” and “LAGACY” is almost a code copy (compare method index()).Is this intended?
To see the mistake:
https://commons.apache.org/proper/commonsmath/apidocs/org/apache/commons/math3/stat/descriptive/rank/Percentile.EstimationType.html
section: Enum Constant Detail
enum: LAGACY
> Wrong equation in Javadoc of Percentile.EstimationType, LAGACY, variable estimation
> 
>
> Key: MATH1347
> URL: https://issues.apache.org/jira/browse/MATH1347
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.6
> Environment: Windows 7
> Reporter: Richard Brunauer
> Priority: Trivial
> Labels: documentation
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> The Javadoc entry for Enum Percentile.EstimationType LAGACY uses a wrong equation for
variable estimate.
> Explaination in version 3.0, 3.6 source code and 3.6 semantics do an interpolation between
two values. The quation for variable estimation has only a ceiling function. This does not
match.

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