function g = alphafunction(x,pos,spoint)
% alpha function.  pos=position; wid=half-width (both scalar)
% lognormal(x,pos,wid), where x may be scalar, vector, or matrix
% pos=position; wid=half-width (both scalar)
% Taekyung Kwon, July 2013  
g = (x-spoint)./pos.*exp(1-(x-spoint)./pos);
for m=1:length(x);if g(m)<0;g(m)=0;end;end