
Accession Number : AD0762419
Title : FORTRAN Subroutines for Bicubic Spline Interpolation
Descriptive Note : Final memorandum rept.
Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC
Personal Author(s) : Cornyn, John J
PDF Url : AD0762419
Report Date : Jun 1973
Pagination or Media Count : 48
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 xy 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.
Descriptors : *COMPUTER PROGRAMS, *INTERPOLATION, APPROXIMATION(MATHEMATICS), SUBROUTINES
Subject Categories : Numerical Mathematics
Computer Programming and Software
Distribution Statement : APPROVED FOR PUBLIC RELEASE