insertion(x)

      function y  = insertion(x)

      n = length(x);
      y = [];
      x = x(:).'; 
      for e = x
        i = find(e<y); 
        if isempty(i)
          y = [ y ; e];
        else    
          y = [y(1:i(1)-1); e; y(i(1):length(y))];
        end;
      end;