function P=pval(cf, x) 
% pval(cf, x)  gets the approximate P value for the given cumulative 
%              function at the given x.  F(). 
if iscf(cf)==0 
   error('invalid cumulative function') 
end 
X=xvals(cf); 
p=pvals(cf); 
x=x(:)'; 
P=zeros(size(x)); 
LB=min(X); 
UB=max(X); 
if isdiscrt(cf)==0 
   R=UB-LB; 
   for i=1:length(x), 
      if x(i)<LB 
         P(i)=0; 
      elseif x(i)>UB 
         P(i)=1; 
      else 
         index=round((x(i)-LB)/R*length(X)+0.5); 
         if index>length(X) 
            index=length(X); 
         end 
         P(i)=p(index); 
      end 
   end 
else 
   for i=1:length(x), 
      index=1; 
      if x(i)<LB 
         P(i)=0; 
      elseif x(i)>=UB 
         P(i)=1; 
      else 
         index=1; 
         while X(index)<=x(i) & index<length(X) 
            index=index+1; 
         end 
         P(i)=p(index-1); 
      end 
   end 
end