Re: st: RE: Xtpoisson and quadchk

[Muhammad Anees <aneesmkhattak@gmail.com>]

One more reason to check for is that the dataset might have repeated
time values within panel. This might lead to error message because an
item can come only once per year in panel data but your data has
repetitions. You can check duplicated values and rerun the commands.

br ship yr_con in 1/n
ship	yr_con
1	2
1	1
1	4
1	3
1	3
1	1
1	2
1	4
2	4
2	2
2	3
2	1
2	1
2	3
2	2
2	4



On 22 March 2011 12:45, Jesper Lindhardsen <JESLIN01@geh.regionh.dk> wrote:
> Hi Garry,
>
> My guess is that it has something to do with how you defined/created
> your 'service' variable as it is indeed your offset if I understand your
> model correctly (exposure(service) = offset(ln(service)) - see help
> -xtpoisson-).
> HTH,
> Jesper
>
>
> Jesper Lindhardsen
> MD, PhD candidate
> Department of Cardiovascular Research
> Copenhagen University Hospital, Gentofte
> Denmark
>
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Garry
> Anderson
> Sent: 22 March 2011 08:31
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Xtpoisson and quadchk
>
> Dear Statalisters,
>
> The message after the -quadchk- command seems a little strange.
> The message is
>
> Refitting model intpoints() =  8
> factor variables and time-series operators not allowed
> in option offset()
> error refitting model
> r(101);
>
> I do not think I am using a factor variable nor a time-series operator,
> and I am not using the offset option.
>
> Any ideas as to the meaning of this message would be appreciated.
>
>
>
>
> . use http://www.stata-press.com/data/r11/ships,clear
>
> . xtpoisson accident op_75_79 co_65_69 co_70_74 co_75_79,
> exposure(service) irr normal
>
> Fitting comparison Poisson model:
>
> Iteration 0:   log likelihood = -147.37993
> Iteration 1:   log likelihood = -80.372714
> Iteration 2:   log likelihood = -80.116093
> Iteration 3:   log likelihood = -80.115916
> Iteration 4:   log likelihood = -80.115916
>
> Fitting full model:
>
> tau =  0.0     log likelihood = -80.115916
> tau =  0.1     log likelihood = -76.060792
> tau =  0.2     log likelihood = -77.535639
>
> Iteration 0:   log likelihood = -76.360754
> Iteration 1:   log likelihood = -75.585665
> Iteration 2:   log likelihood = -74.788481
> Iteration 3:   log likelihood = -74.780993
> Iteration 4:   log likelihood = -74.780982
> Iteration 5:   log likelihood = -74.780982
>
> Random-effects Poisson regression               Number of obs      =
> 34
> Group variable: ship                            Number of groups   =
> 5
>
> Random effects u_i ~ Gaussian                   Obs per group: min =
> 6
>                                                               avg =
> 6.8
>                                                               max =
> 7
>
>                                                Wald chi2(4)       =
> 50.95
> Log likelihood  = -74.780982                    Prob > chi2        =
> 0.0000
>
> ------------------------------------------------------------------------
> ------
>    accident |        IRR   Std. Err.      z    P>|z|     [95% Conf.
> Interval]
> -------------+----------------------------------------------------------
> ------
>    op_75_79 |   1.466677   .1734403     3.24   0.001     1.163259
> 1.849236
>    co_65_69 |   2.032604   .3040933     4.74   0.000     1.516025
> 2.725205
>    co_70_74 |   2.357045   .3998397     5.05   0.000     1.690338
> 3.286717
>    co_75_79 |   1.646935   .3820235     2.15   0.031     1.045278
> 2.594905
>     service | (exposure)
> -------------+----------------------------------------------------------
> ------
>    /lnsig2u |  -2.351868   .8586262    -2.74   0.006    -4.034745
> -.6689918
> -------------+----------------------------------------------------------
> ------
>     sigma_u |   .3085306   .1324562                      .1330045
> .7156988
> ------------------------------------------------------------------------
> ------
> Likelihood-ratio test of sigma_u=0: chibar2(01) =    10.67 Pr>=chibar2 =
> 0.001
>
> . quadchk
>
> Refitting model intpoints() =  8
> factor variables and time-series operators not allowed
> in option offset()
> error refitting model
> r(101);
>
> .
>
> Best wishes, Garry
>
>
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>



-- 
Muhammad Anees
MSc in Economics
The University of Sheffield
United Kingdom

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/