FORTRAN Subroutines for Bicubic Spline Interpolation
Abstract
Two CDC 3800 FORTRAN subroutines (BICUB1 and BICUB2) which perform bicubic spline interpolation of a tabulated function of two variables are described. Given the values X(1),...,X(N) and Y(1),...,Y(M) of two independent variables and the corresponding function values U(I,J)=f(X(I), Y(J)), I=1,...,N and J=1,...,M and certain normal derivatives (optional) along the boundaries of the x-y mesh, BICUB1 estimates the derivatives f(x), f(y), and f(xy) at each (I, J) mesh point. If the normal derivatives along the mesh boundaries are unknown, BICUB1 estimates them using a moving third order two dimensional Lagrange interpolating polynomial. Given the coordinates (XPT, YPT) and the derivatives calculated by BICUB1, BICUB2 obtains the coefficients of the bicubic polynomial for the rectangular region of the mesh containing (XPT, YPT) and estimates the functional value UPT=f(XPT,YPT). In effect, the routines pass a twice continuously differentiable piecewise bicubic polynomial, u(x,y) belongs to (C sup 2), through the given functional values.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1973
- Accession Number
- AD0762419
Entities
People
- John J. Cornyn
Organizations
- United States Naval Research Laboratory