Bivariate data interpolation on regular and irregular
grids, either linear or using splines are the main part of this
package. It is intended to provide FOSS replacement functions for
the ACM licensed akima::interp and tripack::tri.mesh functions.
Linear interpolation is implemented in
interp::interp(..., method="linear"), this corresponds to the call
akima::interp(..., linear=TRUE) which is the default setting and
covers most of akima::interp use cases in depending packages.
A re-implementation of Akimas irregular grid spline
interpolation (akima::interp(..., linear=FALSE)) is now also
available via interp::interp(..., method="akima").
Estimators for partial derivatives are now also available in
interp::locpoly(), these are a prerequisite for the spline interpolation.
The basic part is a GPLed triangulation algorithm (sweep hull
algorithm by David Sinclair) providing the starting point for the
irregular grid interpolator. As side effect this algorithm is also
used to provide replacements for almost all functions of the tripack
package which also suffers from the same ACM license restrictions.
All functions are designed to be backward compatible with their
akima / tripack counterparts.