function values = franke(x,y)
%FRANKE	Franke's test function.
%
%        values = franke(x,y)
%
% returns the values  f(x,y)  of Franke's test function; cf. 
% Richard Franke, A critical comparison of some methods for interpolation of
% scattered data, Naval Postgraduate School Tech.Rep. NPS-53-79-003, 
% March 1979.

% C. de Boor: May 15, 1991
% Copyright (c) 1990-92 by Carl de Boor and The MathWorks, Inc.

values = .75*exp(-((9*x-2).^2 + (9*y-2).^2)/4) + ...
         .75*exp(-((9*x+1).^2)/49 - (9*y+1)/10) + ...
         .5*exp(-((9*x-7).^2 + (9*y-3).^2)/4) - ...
         .2*exp(-(9*x-4).^2 - (9*y-7).^2);
