A general spline differential quadrature method based on quasi-interpolation

The differential quadrature method is a numerical discretization technique for the approximation of derivatives. The classical method is polynomial-based, and there is a natural restriction in the number of grid points involved. A general spline-based method is proposed to avoid this problem. For any degree a Lagrangian spline interpolant is defined having a fundamental function with small support. A quasi-interpolant is used to achieve the optimal approximation order. That two-stage scheme is detailed for the cubic, quartic, quintic and sextic cases and compared with another methods that appear in the literature.