function [g]=DG(param)
% DG  - Derivative of Gaussian function
%
% Usage: g = DG(param)
%
% param = [n,dim,sigma,loc]
% This function creates a function which is the nth derivative
% of a Gaussian of width sigma.  The function is dim long and is
% centered at loc.  Default values are n=0, dim=256, sigma=3, 
% and loc=(dim+1)/2
%

% Written by Jeffrey A Bloom
%
% This function calls the following M-file functions:
% Hermite.m

default=[0,256,3,128.5];
if (nargin<1) 
  param=default; 
elseif (size(param,2)<3)
   param(size(param,2)+1:3) = default(size(param,2)+1:3);  
end
if (size(param,2)<4)
  param(4) = (param(2)+1)/2;
end

n     = param(1);
dim   = param(2);
sigma = param(3);
loc   = param(4);

globalx = 1:dim;
x = globalx-loc;

g = polyval(Hermite(param),x) .* exp(- x.^2/(2*sigma^2));

return

end % function