st: 3D Surface Plot Interpolation

[Joe Canner <jcanner1@jhmi.edu>]

At the recent Stata Conference "wishes and grumbles" session, several of us expressed interest in 3D Surface plots.  StataCorp did not give much reason for optimism in this area.  There is currently a user-written module "surface" which does an OK job of 3D surface plots, but does not have a feature for interpolating and smoothing. 

In SAS, for example, there is PROC G3GRID, which provides a data set with interpolated/smoothed points which can then be plotted with PROC G3D.  G3GRID uses, among other methods, an interpolation method by Akima (1978) which involves forming triangles with existing (x,y) points, fitting a quintic bivariate polynomial for the three vertices of the triangle, and using the resulting model to fill in additional interpolated points.  

There is a set of Fortran subroutines for this algorithm and I would like to try my hand at converting them to Mata, but before I spend a lot of time doing that, is anybody aware of existing Stata functions or commands (user-written or native) that are available for this?

Thanks,
Joe Canner
Johns Hopkins University School of Medicine
Department of Surgery

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