What method does the Spatial Heat Map Data Function tool on the TIBCO Community site use to generate the heat map?

What method does the Spatial Heat Map Data Function tool on the TIBCO Community site use to generate the heat map?

What method does the Spatial Heat Map Data Function tool on the TIBCO Community site use to generate the heat map?
  The interactive Spatial Heat Map Data Function tool is at the following URL on the TIBCO Community site:

     https://community.tibco.com/modules/spatial-heat-map-data-function-tibco-spotfirer

It fits a local regression model to the data, using a call to the loess() function in TIBCO Enterprise Runtime for R (TERR). This is the call to loess() at the core of the data function's TIBCO Enterprise Runtime for R (TERR) script: 

      loess(z~x*y, data=xyzdata, span=smooth.scale, na.action=na.exclude)

A loess model is a form of non-parametric regression where the regression surface is locally approximated by polynomials of degree 1 or 2. The TERR script's call to loess() uses the function's default polynomial degree of 2, so the data function is using locally-quadratic fitting to generate the regression surface for the heat map and its contours.