Hi Eric.
On Wed, 31 Jan 2018 10:17:48 +0100, Eric Barnhill wrote:
If we are going to target Java 8 with commons-statistics, then we
should
make use of the built in DoubleSummaryStatistics() (
https://docs.oracle.com/javase/8/docs/api/java/util/DoubleSummaryStatistics.html)
class, related classes for other numeric types, and related
interfaces in
the Collectors() class.
Thanks for taking this on.
I see a clear niche within commons for a convenience class that
allows the
user to simply pass an array and a requested statistic, rather than
build a
stream. Overloaded methods ( for example getMean(double[] d) and
getMean(long[] l) ) would handle whether, for example,
DoubleSummaryStatistics or LongSummaryStatistics need be called and
the
return value could simply be the desired statistic.
Do you also intend to look into generics (e.g. allowing statistics
on objects like "Duration", as suggested by Gary some time ago)?
That would take care of Mean, Min, Max Sum, and Count.
I think the rest of the summary stats can be gathered by mapping
intermediate operations onto the same streams. For example, mapping
each
value onto its square before calling SummaryStatistics(), then
dividing the
sum of the mapped stream by its count, would return standard
deviation.
That also seems to me a nice niche for commons, delivering additional
summary statistics beyond the built-ins.
Given that a lot of the key functionality is built-in the scope of
this
project seems better suited for a SummaryStatistics class with static
methods.
As long as it does not block fluent usage of Java 8 interfaces and
syntactic constructs...
If this sounds good I'll start a branch to develop it.
I'm still not a very knowledgeable user of JDK8 (a hidden cost of years
working on CM).
I hope that others will comment (and help with) the revamping of
the statistical utilities.
Regards,
Gilles
Eric
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