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  1. Commons Math
  2. MATH-224

Utility method to aggregate Statistics

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Details

    • Improvement
    • Status: Closed
    • Minor
    • Resolution: Fixed
    • None
    • 2.0
    • None
    • None

    Description

      Below is the conversation related to this topic that was posted to the Commons Users group.

      -------------------------------------------------

      Hi,

      >
      > I'm writing a complex validation algorithm, that makes a K-Fold
      > cross-validation using a data set. The data set is partitioned into K
      > subsamples, and of the K subsamples, a single subsample is retained
      > as the validation data for testing, and the remaining K − 1
      > subsamples are used as training data. The process is then repeated K
      > times, and at the end the K results are aggregated to a single
      > result. The problem is that all K results return Statistics objects
      > (org.apache.commons.math.stat.descriptive.SummaryStatistics), and I
      > need to make the aggregation of all K objects in a single Statistics.
      > I think it is a common problem in the statistics field. There's
      > anyone who had already implemented an utility method to do it?

      There is no such feature currently in commons-math. The
      SummaryStatistics class wraps a bunch of specialized statistics classes
      (Sum, Mean, Max, SumOfSquares ...) which can be overriden by
      user-provided StorelessUnivariateStatistic implementations.

      So this feature should be added to the StorelessUnivariateStatistic
      interface and all its implementations, with a signature like this:
      public void aggregate(StorelessUnivariateStatistic otherStatistic);

      The implementation of this method should only use the
      StorelessUnivariateStatistic methods, i.e. getResult() and getN(). This
      seems feasible for the statistics used by SummaryStatistics, but has not
      been done yet.

      One should be aware that SummaryStatistics does not enforce strong
      typing, so one could call aggregate on a Sum instance and provide it a
      Min instance, which would of course result in meaningless results.

      > Or maybe it would be interesting to request it as an Improvement to
      > the Commons Math developers, adding an "aggregator" to all Statistics
      > implementations?

      If you want to request this improvement, please open a ticket for it
      using our JIRA tracking system:
      http://issues.apache.org/jira/browse/MATH. You'll have to register to be
      able to add your feature request. You can also provide a patch if you
      want to contribute it by yourself.

      Luc

      >
      > Thanks in advance,
      >
      > Andre Panisson

      Attachments

        1. commons_math.patch
          23 kB
          Andre Panisson
        2. math_224.patch
          13 kB
          John Bollinger
        3. math_224-descriptive.patch
          20 kB
          John Bollinger

        Activity

          People

            psteitz Phil Steitz
            panisson Andre Panisson
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            Dates

              Created:
              Updated:
              Resolved: