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https://issues.apache.org/jira/browse/STATISTICS-94?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alex Herbert updated STATISTICS-94:
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Component/s: descriptive
> Support median and quantile for long datatype
> ---------------------------------------------
>
> Key: STATISTICS-94
> URL: https://issues.apache.org/jira/browse/STATISTICS-94
> Project: Commons Statistics
> Issue Type: Improvement
> Components: descriptive
> Reporter: Alex Herbert
> Assignee: Alex Herbert
> Priority: Minor
>
> Add support to the {{Median}} and {{Quantile}} class for the {{long}}
> datatype. Current support is for {{double[]}} and {{{}int[]{}}}. Via
> primitive conversion these support float, short, char and byte if an array is
> appropriately converted. However {{long}} cannot be supported by primitive
> conversion.
> The current median and quantile result is returned as a {{{}double{}}}. This
> is not appropriate for the result on a long array as the closest
> representable double may be outside the range of the input data if the data
> have more than 53-bits in their integer representation. However if the
> integer value is representable as less than 53-bits then the double will
> provide a fractional part that cannot be returned if the result was a long. I
> suggest using the {{StatisticResult}} for the return value allowing both
> double and long representations:
> {code:java}
> StatisticResult r = Median.of(new long[] {Long.MIN_VALUE, Long.MAX_VALUE});
> r.getAsDouble(); // -0.5
> r.getAsLong(); // 0{code}
> h2. Rounding
> The current behaviour for {{StatisticResult}} is to return the integer
> representations using the closest representation of the floating-point value
> with ties towards positive infinity. So in the example above the median as a
> long is 0.
> This behaviour could be changed with a rounding mode parameter. Unfortunately
> the current rounding behaviour is not represented by any mode in
> [java.math.RoundingMode (Javadoc JDK
> 21)|https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/math/RoundingMode.html]
> so this enum cannot be reused to set the mode. The rounding behaviour
> matches [java.lang.Math.round(double) (Javadoc JDK
> 21)|https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Math.html#round(double)].
> The closest match is RoundingMode.HALF_UP when above zero and
> RoundingMode.HALF_DOWN when below zero. If rounding to nearest is only
> concerned with the 0.5 boundary then support for rounding could add modes for
> rounding ties towards: negative infinity; positive infinity: or zero
> (floating-point truncation).
>
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