各位：
我用一下的一段程序进行VAR模型的规划求解，但是总是说没有解？？？
请问是什么原因呢？万分感激！！！
!VaR Model;
Model:

   Sets:
     Periods/Period1..Period218/:X,Y;!Define the array Periods;
     Stocks/Stock1..Stock21/:Weight;!Define the array Stocks;
     LINKS(Periods,Stocks):Return;!The return of 21 stocks in 218 weeks;
      
   Endsets

   Data:
   [email=Return=@OLE(]Return=@OLE('E:lingo\var\In[/email] Smaple Stock Return Matrix.xls','ReturnMatrix');!Import the data from excel;
   a=0.1;!Define5 the significance level;
   RVar=-0.055;!Define the RVar;   
   Enddata
   
    Max=(1/218)*@sum(Periods(I):X(I));
   @for(Stocks(J):Weight(J)>=0);!the weight is larger than zero, short is not allowed;
   @sum(Stocks(J):Weight(J))=1;!the sum of weights of stocks equals to 1;
   @for(Periods(I):@bin(Y(I)));!the yi is integer 0 or 1;
   @for(Periods(I):@sum(Stocks(J):Weight(J)*Return(I,J))=X(I));
   @sum(Periods(I):1-Y(I))*(1/218)<=a;
   Rmin=@min(Periods(I):X(I));!Rmin is the smallest return in 218 weeks for the portifolio;
   @for(Periods(I):Rmin+(Rvar-Rmin)*Y(I)<=X(I));

end