TOMS886, a C library which implements an interpolation procedure based on "Padua points", defined in the square [-1,+1]^2, whose interpolating power is especially good. It is possible to map these points to the general rectangle, ellipse or triangle to do interpolation on these regions as well.
The text of many ACM TOMS algorithms is available online through ACM: http://calgo.acm.org/ or NETLIB: http://www.netlib.org/toms/index.html.
The computer code and data files made available on this web page are distributed under the GNU LGPL license.
TOMS886 is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version.
LAGRANGE_INTERP_2D, a C library which defines and evaluates the Lagrange polynomial p(x,y) which interpolates a set of data depending on a 2D argument that was evaluated on a product grid, so that p(x(i),y(j)) = z(i,j).
PWL_INTERP_2D, a C library which evaluates a piecewise linear interpolant to data defined on a regular 2D grid.
PWL_INTERP_2D_SCATTERED, a C library which evaluates a piecewise linear interpolant to data which is available at an irregularly arranged set of points.
RBF_INTERP_2D, a C library which defines and evaluates radial basis function (RBF) interpolants to 2D data.
SHEPARD_INTERP_2D, a C library which defines and evaluates Shepard interpolants to scattered 2D data, based on inverse distance weighting.
TEST_INTERP_2D, a C library which defines test problems for interpolation of regular or scattered data z(x,y), depending on a 2D argument.
TRIANGLE_INTERPOLATE, a C library which shows how vertex data can be interpolated at any point in the interior of a triangle.
VANDERMONDE_INTERP_2D, a C library which finds a polynomial interpolant to data z(x,y) of a 2D argument by setting up and solving a linear system for the polynomial coefficients, involving the Vandermonde matrix.
Marco Caliari, Stefano de Marchi, Marco Vianello.