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From "X. B. (JIRA)" <j...@apache.org>
Subject [jira] Created: (MATH-504) LOESS interpolation & tricube fonction
Date Mon, 31 Jan 2011 15:09:18 GMT
LOESS interpolation & tricube fonction
--------------------------------------

                 Key: MATH-504
                 URL: https://issues.apache.org/jira/browse/MATH-504
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 2.1
         Environment: Win XP
            Reporter: X. B.
            Priority: Trivial


the doc for tricube fonction used in LOESS smooth() says :

* @return <code>(1 - |x|<sup>3</sup>)<sup>3</sup></code>.
But I'dont see the absolute value for x.

Also, the "classical" tricube fonction (see http://www.itl.nist.gov/div898/handbook/pmd/section1/pmd144.htm)
seems to return 0 if abs(x)>1. 
In the code of the tricube method, It is apparently not the case...


    private static double tricube(final double x) {
        final double tmp = 1 - x * x * x;
        return tmp * tmp * tmp;
    }

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