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From Phil Steitz <>
Subject Re: Bug (and fix) on Commons-Math SplineInterpolator
Date Fri, 02 Apr 2004 22:35:17 GMT
Should be fixed now in CVS.

In addition to fixing the impl, I made the following changes:

SplineInterpolator.interpolate(double[], double[]) now returns a 
PolynomialSplineInterpolator (new class), which has an array of 
PolynomialFunctions representing the spline segments.

Both PolynomialSplineInterpolator and PolynomialFunction implement the new 
DifferentiableUnivariateRealFunction interface. 
PolynomialSplineInterpolator exposes its polynomials and knot point arrays 
as read-only properties (getters return copies).

I added tests to SplineInterpolatorTest (replaces InterpolatorTest) to 
verify that the correct coefficients are being computed (in the 
"degenerate" cases, testing against analytical values, for the sin case, 
using R as a reference) and that the PolynomialSplineFunctions give 
consistent values at the knot points and the polynomials "match up" (agree 
throgh 2 derivatives) at the knot points.


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