Weighted Derivative Histopolation on Arbitrary Grids: Admissibility and Exact Factorizations

In this paper, we introduce a weighted derivative histopolation framework on families of intervals.

The degrees of freedom consist of one scalar normalization and weighted integral moments of the derivative over a prescribed family of subintervals.

We prove that the resulting scheme is unisolvent on $\Pi_N$ when the interval family separates polynomials of degree at most $N-1$ through weighted moments and the normalization is nonzero on constants.

Thus, the derivative moments determine the polynomial up to an additive constant, and the scalar normalization fixes this remaining degree of freedom.

This gives a sharp criterion for the well-posedness of the interpolation problem and a complete characterization of the admissible scalar normalizations.

We then show how admissible families of intervals can be constructed from a fixed grid.

When the endpoints of the intervals belong to the grid, admissibility is reduced to the nonsingularity of an interval matrix associated with the family, which depends only on the representation of the intervals in terms of consecutive cells.

For Jacobi weights, the associated data matrices have a natural block structure in Jacobi polynomial bases, and the reduced derivative matrix can be expressed in terms of shifted Jacobi moment matrices.

We next study Chebyshev configurations in which this structure becomes explicit.

For the four classical Chebyshev families, suitable polynomial bases lead to diagonal Gram matrices for the reduced derivative matrices.

We show that this diagonal structure depends on the simultaneous choice of the weight, the basis, and the grid.

Numerical experiments on equispaced and Chebyshev--Lobatto nodes show the behaviour of the method for different interval families and for different Jacobi parameters.