function err = log_gauss_errfn(fitparams,x,y);
%
% function err = log_gauss_errfn(fitparams,x,y);
% 
% Returns the error, err, between the z-gaussian function and the 
% input data.  Assumes the input data is of the form where x is 
% the grid, and y is the Gaussian.
%
% Input variable fitparams should be of the following form:
%
% fitparams = [A, xo, sigma], 
%
% where we are fitting to a gaussian of the form:
%
% log(y) = log(A*exp(-(x-xo)^2 / (2*sigma^2)))
%	 = log(A) - (x-xo)^2 / (2*sigma^2);
%
%
% Written by Miles A. Sundermeyer, 2/1/06

% parse fitparams
A = fitparams(1);
xo = fitparams(2);
sigma = fitparams(3);

% compute the function associated with the fit params
logy = log(y);
logyfit =  log(A*exp(-(x-xo).^2 / (2*sigma^2)));

vecscale = 3e+2;

if(0)
  % plot this as a check
  figure(199)
  clf

  plot(x,logy,'bo');
  hold on
  plot(x,exp(logyfit),'r-');
  xlabel('x')
  ylabel('y')
  axis([min(x(:)) max(x(:)) min([min(y(:)) 0]) max(y(:))])
end

% compute the error between the fitted and actual fields
err = mean(abs([logy(:)-logyfit(:)]));
%drawnow
%pause(0.1)