function pf=getpf(cf) 
% getpf(cf)  Generates a pdf or pmf from a cumulative function. 
% 
%    The algoryth used by this function sometimes display oscillatory 
%    behavior - basically, this function is not %100 reliable.  If the 
%    probability function getpf spits out looks like a failure, you can us 
%    the smooth function to try and salvage it. 
if iscf(cf)==0 
   error('invalid cumulative function') 
end 
x=xvals(cf); 
p=pvals(cf); 
newp=zeros(length(p), 1); 
if isdiscrt(cf)==1 
   P=0; 
   for i=1:(length(x)), 
      newp(i)=p(i)-P; 
      P=p(i); 
   end 
else 
   P=(p(2)-p(1))/(x(2)-x(1)); 
   newp(1)=P; 
   for i=2:length(x), 
      dx=x(i)-x(i-1); 
      P=2*(p(i)-p(i-1))/dx-P; 
      if P<0 
         P=0; 
      end 
      newp(i)=P; 
   end 
end 
pf=[cf(1,1) 1; x' newp]; 
if ispf(pf)==0 
   newp=newp./ttlprob(pf); 
   pf=[cf(1,1) 1; x' newp]; 
end