function plotf(pf, fs) 
% plotf(pf, fs)  Plot function for probability and cumulative functions. 
%    The optional format string fs is passed to the MATLAB plot functions. 
if nargin==1 
   fs='-'; 
end 
if ispf(pf)==1 
   x=xvals(pf); 
   p=pvals(pf); 
   if isdiscrt(pf)==1 
      stem(x,p,fs); 
   else 
      plot(x,p,fs); 
   end 
elseif iscf(pf)==1 
   x=xvals(pf); 
   p=pvals(pf); 
   if isdiscrt(pf)==1 
      i=length(x); 
      x=[x(1)-(x(2)-x(1)) x x(i)+(x(i)-x(i-1))]; 
      p=[0 p 1]; 
      stairs(x,p,fs); 
   else 
      plot(x,p,fs); 
   end 
else 
   error('not a valid probability or cumulative function') 
end