st: "no observations"

[Scott Cunningham <scunning@gmail.com>]

Anyone know why I keep getting this error.  I ask because it's  
impossible that I have "no observations," since I just ran the  
poisson MLE procedure prior to executing -mfx-.  So I'm not sure  
what's going on here.

.  xi:xtpoisson rp srfm age2 hgc hhd1 i.census i.year  
i.census*i.year, fe i(id)


>  vce(boot);
i.census          _Icensus_1-4        (naturally coded; _Icensus_1  
omitted)
i.year            _Iyear_1998-2002    (naturally coded; _Iyear_1998  
omitted)
i.cen~s*i.year    _IcenXyea_#_#       (coded as above)
(running xtpoisson on estimation sample)

Bootstrap replications (50)
----+--- 1 ---+--- 2 ---+--- 3 ---+--- 4 ---+--- 5
..................................................    50

Conditional fixed-effects Poisson regression    Number of obs       
=      1905
Group variable (i): id                          Number of groups    
=       636

                                                Obs per group: min  
=         2
                                                               avg  
=       3.0
                                                               max  
=         3

                                                Wald chi2(15)       
=     53.50
Log likelihood  = -3527.8153                    Prob > chi2         
=    0.0000

------------------------------------------------------------------------ 
------
             |   Observed   Bootstrap                         Normal- 
based
          rp |      Coef.   Std. Err.      z    P>|z|     [95% Conf.  
Interval]
------------- 
+----------------------------------------------------------------
        srfm |   .0139139   .0078909     1.76   0.078     -. 
001552    .0293799
        age2 |  -.0259416   .0117042    -2.22   0.027    -.0488814    
-.0030018
         hgc |   .1280376    .064077     2.00   0.046      . 
002449    .2536261
        hhd1 |  -.4210113   .2767025    -1.52   0.128    -. 
9633383    .1213156
  _Icensus_2 |  -.5786532   .5795236    -1.00   0.318     
-1.714499    .5571921
  _Icensus_3 |  -.7181931   .7184449    -1.00   0.317     
-2.126319    .6899329
  _Icensus_4 |  -1.209667   .6757717    -1.79   0.073     
-2.534155    .1148217
 _Iyear_2000 |   1.316794   .9342833     1.41   0.159    -. 
5143679    3.147955
 _Iyear_2002 |   3.629465   1.789771     2.03   0.043     . 
1215795    7.137351
_Icen~2_2000 |   .6065933   .4341424     1.40   0.162    -.2443102     
1.457497
_Icen~2_2002 |  -.1306399   .3759929    -0.35   0.728    -. 
8675724    .6062925
_Icen~3_2000 |   .6894538   .3806239     1.81   0.070    -.0565554     
1.435463
_Icen~3_2002 |  -.0121621   .3575348    -0.03   0.973    -. 
7129175    .6885933
_Icen~4_2000 |   .8719567   .4199848     2.08   0.038     .0488016     
1.695112
_Icen~4_2002 |   .7304281    .594425     1.23   0.219    -. 
4346235     1.89548
------------------------------------------------------------------------ 
------

.  mfx, dydx varlist(srfm age age2 hgc hhd1);
no observations
r(2000);

end of do-file
r(2000);


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