Franke's bivariate test function
z = franke(x,y)
z = franke(x,y) returns
z(i) of Franke's function at the site
z of the same size as
must be of the same size).
Franke's function is the following weighted sum of four exponentials:
The following commands provide a plot of Franke's function:
pts = (0:50)/50; [x,y] = ndgrid(pts,pts); z = franke(x,y); surf(x,y,z), view(145,-2), set(gca,'Fontsize',16)
 Richard Franke. “A critical comparison of some methods for interpolation of scattered data.” Naval Postgraduate School Tech.Rep. NPS-53-79-003, March 1979.