我在用rats做多元garch时,想使用t分布,其中有个参数shape应该如何设置,默认说是blank(估计值替代),但用输入空格,出来的结果很怪异,没有对数似然值,另外系数值也很奇怪:
MV-GARCH, DCC - Estimation by BFGS
Convergence in 1 Iterations. Final criterion was 0.0000000 <= 0.0000100
Usable Observations 356
Log Likelihood NA
Variable Coeff Std Error T-Stat Signif
************************************************************************************
1. C(1) 0.0002135418 0.0000000000 0.00000 0.00000000
2. C(2) 0.0002315204 0.0000000000 0.00000 0.00000000
3. A(1) 0.0500000000 0.0000000000 0.00000 0.00000000
4. A(2) 0.0500000000 0.0000000000 0.00000 0.00000000
5. B(1) 0.7500000000 0.0000000000 0.00000 0.00000000
6. B(2) 0.7500000000 0.0000000000 0.00000 0.00000000
7. DCC(1) 0.2000000000 0.0000000000 0.00000 0.00000000
8. DCC(2) 0.2000000000 0.0000000000 0.00000 0.00000000
如果shape设置为1:结果如下:
Convergence in 1 Iterations. Final criterion was 0.0000000 <= 0.0000100Usable Observations 356
Log Likelihood NA
Variable Coeff Std Error T-Stat Signif************************************************************************************
1. C(1) 0.0002135418 0.0000000000 0.00000 0.00000000
2. C(2) 0.0002315204 0.0000000000 0.00000 0.00000000
3. A(1) 0.0500000000 0.0000000000 0.00000 0.00000000
4. A(2) 0.0500000000 0.0000000000 0.00000 0.00000000
5. B(1) 0.7500000000 0.0000000000 0.00000 0.00000000
6. B(2) 0.7500000000 0.0000000000 0.00000 0.00000000
7. DCC(1) 0.2000000000 0.0000000000 0.00000 0.00000000
8. DCC(2) 0.2000000000 0.0000000000 0.00000 0.00000000
如果设置为356,结果如下:
GARCH(P=1,Q=1,MV=DCC,DIST=T,SHAPE=356,NOMEAN,ITERS=800) 3 358 RE_SF RE_FS
MV-GARCH, DCC - Estimation by BFGSNO CONVERGENCE IN 19 ITERATIONSLAST CRITERION WAS 0.0000000SUBITERATIONS LIMIT EXCEEDED.ESTIMATION POSSIBLY HAS STALLED OR MACHINE ROUNDOFF IS MAKING FURTHER PROGRESS DIFFICULTTRY HIGHER SUBITERATIONS LIMIT, TIGHTER CVCRIT, DIFFERENT SETTING FOR EXACTLINE OR ALPHA ON NLPARRESTARTING ESTIMATION FROM LAST ESTIMATES OR DIFFERENT INITIAL GUESSES MIGHT ALSO WORK
Usable Observations 356
Log Likelihood 2408.8605
Variable Coeff Std Error T-Stat Signif
************************************************************************************
1. C(1) 9.5383e-005 5.3630e-006 17.78537 0.00000000
2. C(2) 1.1326e-004 6.0865e-006 18.60911 0.00000000
3. A(1) -0.0509 2.0171e-004 -252.18416 0.00000000
4. A(2) -0.0675 2.8525e-003 -23.64648 0.00000000
5. B(1) 0.6242 0.0159 39.21562 0.00000000
6. B(2) 0.6171 0.0208 29.66694 0.00000000
7. DCC(1) 0.0350 4.8529e-003 7.21623 0.00000000
8. DCC(2) 2.2464e-014 0.2004 1.12106e-013 1.00000000
请各位大侠指教,参数设置界面如下: