function spf=standard(pf) 
% standard(pf)  generates a stardardized probability function 
if ispf(pf)==0 
   error('invalid pf') 
end 
x=xvals(pf); 
p=pvals(pf); 
newx=(x-mmean(pf))./sqrt(var(pf)); 
spf=[pf(1,:); newx' p']; 
p=p./ttlprob(spf); 
spf=[pf(1,:); newx' p'];