. stthreg, lny0() mu()

         failure _d:  rate
   analysis time _t:  year

initial:       log likelihood = -468.10846
alternative:   log likelihood = -9963.7034
rescale:       log likelihood = -468.10846
rescale eq:    log likelihood = -316.68203
Iteration 0:   log likelihood = -316.68203  (not concave)
Iteration 1:   log likelihood = -299.45475  
Iteration 2:   log likelihood = -282.47602  
Iteration 3:   log likelihood = -251.35666  (not concave)
Iteration 4:   log likelihood = -245.39685  (not concave)
Iteration 5:   log likelihood = -244.49748  
Iteration 6:   log likelihood = -244.48078  
Iteration 7:   log likelihood = -224.38572  (not concave)
Iteration 8:   log likelihood = -223.94535  
Iteration 9:   log likelihood = -219.33501  
Iteration 10:  log likelihood = -213.74321  
Iteration 11:  log likelihood = -213.59611  (backed up)
Iteration 12:  log likelihood = -213.56756  (backed up)
Iteration 13:  log likelihood = -213.55221  (backed up)
Iteration 14:  log likelihood = -213.54944  (backed up)
Iteration 15:  log likelihood = -213.54832  (backed up)
Iteration 16:  log likelihood = -213.54809  (backed up)
Iteration 17:  log likelihood = -213.54806  (backed up)
Iteration 18:  log likelihood = -213.54805  (backed up)
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
Iteration 19:  log likelihood = -213.54805  (not concave)
Iteration 20:  log likelihood =   -212.476  
Iteration 21:  log likelihood = -212.35334  (backed up)
Iteration 22:  log likelihood = -212.35239  (backed up)
Iteration 23:  log likelihood = -212.35233  (backed up)
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
Iteration 24:  log likelihood = -212.35232  (backed up)
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
Iteration 25:  log likelihood = -212.35232  (backed up)
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
Iteration 26:  log likelihood = -212.35232  (backed up)
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
Iteration 27:  log likelihood = -212.35232  (not concave)
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
Iteration 28:  log likelihood = -212.35232  
could not calculate numerical derivatives
missing values encountered
我在做时间序列的门限回归，出现这种情况到底怎么回事？