Class NonnegativityPreservingCubicSplineInterpolator

  • public class NonnegativityPreservingCubicSplineInterpolator
    extends PiecewisePolynomialInterpolator
    Filter for nonnegativity of cubic spline interpolation based on R. L. Dougherty, A. Edelman, and J. M. Hyman, "Nonnegativity-, Monotonicity-, or Convexity-Preserving Cubic and Quintic Hermite Interpolation" Mathematics Of Computation, v. 52, n. 186, April 1989, pp. 471-494. First, interpolant is computed by another cubic interpolation method. Then the first derivatives are modified such that non-negativity conditions are satisfied. Note that shape-preserving three-point formula is used at endpoints in order to ensure positivity of an interpolant in the first interval and the last interval