Interpolation Routines

INTERP is a FORTRAN77 library which takes a set of data associated with successive values of a parameter, and produces an interpolating function which can be evaluated over a continuous range of the parameter.


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


INTERP 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:

BERNSTEIN_POLYNOMIAL, a FORTRAN77 library which evaluates the Bernstein polynomials, useful for uniform approximation of functions;

DIVDIF, a FORTRAN77 library which uses divided differences to interpolate data.

HERMITE, a FORTRAN77 library which computes the Hermite interpolant, a polynomial that matches function values and derivatives.

NMS, a FORTRAN77 library which includes a package for the computation of piecewise cubic Hermite splines.

PPPACK, a FORTRAN77 library which implements Carl de Boor's piecewise polynomial functions, including, in particular, cubic splines.

RBF_INTERP, a FORTRAN77 library which defines and evaluates radial basis interpolants to multidimensional data.

SPLINE, a FORTRAN77 library which computes functions that approximate or interpolate data.

TEST_APPROX, a FORTRAN77 library which defines a number of test problems for approximation and interpolation.

TEST_INTERP_1D, a FORTRAN77 library which defines test problems for interpolation of data y(x), depending on a 1D argument.


  1. Samuel Conte, Carl deBoor,
    Elementary Numerical Analysis,
    Second Edition,
    McGraw Hill, 1972,
    ISBN: 07-012446-4,
    LC: QA297.C65.

Source Code:

Examples and Tests:

List of Routines:

You can go up one level to the FORTRAN77 source codes.

Last revised on 28 February 2014.