function chi2 = nchisq(x,f,m,s);
% nchisq.m 1/23/06 (; removed from lines 12-15)
% function chi2 = nchisq(x,f,m,s)
% Calculates chi square of the fit of a Normal
% distribution with mean m and standard deviation
% s to data grouped into the equal size classes
% defined by the vector x, with frequencies given
% by the vector f
ni = length(x) - 1;    % number of classes
N = sum(f);            % total frequency
p = 0.5 + 0.5*erf((x-m)/(sqrt(2)*s));  % cum norm prob of class limits
pt = p(ni+1) - p(1)   % total probability in classes
p2 = p(2:ni+1)
pc = p2 - p(1:ni)     % prob of each class
fc = pc*N*pt;         % theoretical frequency in each class
chi2 = sum((f - fc).^2./fc); % calculate Chi Square