Piecewise Linear Interpolation in 2D for Gridded Data

PWL_INTERP_2D is a C which evaluates a piecewise linear interpolant of data depending on a 2D argument, defined on on a product grid, so that p(x(i),y(j)) = z(i,j).

PWL_INTERP_2D requires the R8LIB library. The test code requires the TEST_INTERP_2D library.


The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.


PWL_INTERP_2D is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

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).

PADUA, a C library which returns the points and weights for Padu sets, useful for interpolation in 2D. GNUPLOT is used to plot the points.

PWL_INTERP_1D, a C library which interpolates a set of data using a piecewise linear function.

R8LIB, a C library which contains many utility routines using double precision real (R8) arithmetic.

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 2D data, based on inverse distance weighting.

TEST_INTERP_2D, a C library which defines test problems for interpolation of data z(x,y), depending on a 2D argument.

TOMS886, a C library which defines the Padua points for interpolation in a 2D region, including the rectangle, triangle, and ellipse, by Marco Caliari, Stefano de Marchi, Marco Vianello. This is a C version of ACM TOMS algorithm 886.

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.


  1. Kendall Atkinson,
    An Introduction to Numerical Analysis,
    Prentice Hall, 1989,
    ISBN: 0471624896,
    LC: QA297.A94.1989.
  2. Philip Davis,
    Interpolation and Approximation,
    Dover, 1975,
    ISBN: 0-486-62495-1,
    LC: QA221.D33
  3. David Kahaner, Cleve Moler, Steven Nash,
    Numerical Methods and Software,
    Prentice Hall, 1989,
    ISBN: 0-13-627258-4,
    LC: TA345.K34.

Source Code:

Examples and Tests:

List of Routines:

You can go up one level to the C source codes.

Last revised on 15 October 2012.