久期回归结果出现omitted

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收藏 2015-06-07

我用久期回归，结果出现omitted，请问这究竟是怎么回事呢？图片不会上传，nv1和czhen1的回归结果都是omitted
No. of subjects =       3448                   Number of obs =    3448
No. of failures =       378
Time at risk =  20882.04447
                                                LR chi2(6)    = 131.10
Log likelihood  = -1131.8172                   Prob > chi2    = 0.0000

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      _t |    Coef. Std. Err.    z P>|z|    [95% Conf. Interval]
-------------+----------------------------------------------------------------
      nan1 |  -.1196925 .0298952 -4.00 0.000 -.1782859 -.061099
      nv1 |       0  (omitted)
   ncun1 |  -.2273449 .0724134 -3.14 0.002 -.3692726 -.0854173
   czheng1 |       0  (omitted)
      age | .0001622 .000434    0.37 0.709 -.0006883 .0010128
      cjy |  -.2480775 .0508666 -4.88 0.000 -.3477741 -.1483808
      zjy |  -.2910971 .0357644 -8.14 0.000    -.361194 -.2210003
      gjy |  -.1946388 .0638065 -3.05 0.002 -.3196973 -.0695804
   _cons |  -2.707051 .1765852 -15.33 0.000 -3.053151 -2.36095
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