function histo(X, pf, n) 
% histo(X, pf, n)  Plots a cumulative histogram of all samples and 
%    experiments in the random variable matrix X against an associated 
%    probability function specified by pf.  pf may be a probability or 
%    cumulative function.  n is the number of bars in the histogram.  n is 
%    not needed for discrete probability function, and is optional for 
%    continuous one.  The default value for n is 10.  X does not have to be 
%    a matrix: it may be a vector.  If pf is an empty matrix [], no function 
%    will be plotted. 
% 
%    The resulting plot represents a mass, density, or distribution 
%    function. 
if nargin==2 
   n=10; 
end 
if ~(pf==[]) 
   if iscf(pf)==0 & ispf(pf)==0 
      error('pf is not a valid function') 
   end 
end 
rv=X(:)'; 
if pf==[] 
   [N, x]=hist(rv, n); 
   N=N./length(rv); 
elseif iscf(pf) 
   cf=pf; 
   if isdiscrt(cf)==0 
      [N, x]=hist(rv, n); 
   else 
      [N, x]=hist(rv, xvals(cf)); 
   end 
   N=N./length(rv); 
   if isdiscrt(cf)==0 
      N=(N.*n)./(max(rv)-min(rv)); 
   end 
   CN=N; 
   for i=2:length(N), 
      CN(i)=CN(i)+CN(i-1); 
   end 
   N=CN; 
else 
   if isdiscrt(pf)==0 
      [N, x]=hist(rv, n); 
   else 
      [N, x]=hist(rv, xvals(pf)); 
   end 
   N=N./length(rv); 
   if isdiscrt(pf)==0 
      N=(N.*n)./(max(rv)-min(rv)); 
   end 
end 
bar(x, N, 'r') 
hold on 
if ~(pf==[]) 
   plotf(pf) 
end 
hold off