function S=expmod(x,p)
% EXPMOD a m-function to calculate the semivariance using an exponential
%	model. This function is used in conjunction with NLLEASQR.M to
%	provide a non-linear least square fit to emprically derived 
%	semivariance estimates (from the data).
%
% SYNTAX:
%	S=expmod(x,p)
%
% The parameter order is as follows:
%	p(1)=nugget
%	p(2)=sill
%	p(3)=range
%
% Started 1999:02:09 D. Glover, WHOI
% Modif'd 1999:05:12 DMG to provide two forms of exponential model
% Modif'd 1999:05:13 DMG to improve the "help" instructions

% This is the "adjusted" sill form (used by Fuentes)

S=p(1)+(p(2)-p(1))*(1-exp(-x./p(3)));

% This is the more convential form

%S=p(1)+p(2)*(1-exp(-x./p(3)));