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| From | Garry Anderson <g.anderson@unimelb.edu.au> |
| To | <statalist@hsphsun2.harvard.edu> |
| Subject | RE: st: RE: Xtpoisson and quadchk |
| Date | Tue, 22 Mar 2011 19:42:01 +1100 |
Thank you Jesper and Anees for your suggestions.
The service variable is a continuous variable with a range of 45 to 44882. This seems usual for an exposure variable. Note that the datafile is the example in the Stata manual
use http://www.stata-press.com/data/r11/ships,clear
. codebook service
--------------------------------------------------------------------------------------------------
service (unlabeled)
--------------------------------------------------------------------------------------------------
type: numeric (float)
range: [45,44882] units: 1
unique values: 33 missing .: 6/40
mean: 4811
std. dev: 9644.17
percentiles: 10% 25% 50% 75% 90%
127 349 1095 2244 17176
. sum service
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
service | 34 4811 9644.166 45 44882
Best wishes , Garry
-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Muhammad Anees
Sent: Tuesday, 22 March 2011 7:27 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: RE: Xtpoisson and quadchk
I would further the idea of jesper, if your offset or exposure variable is categorical, you might have received the error. Check if your service is not in (0,1) form.
best
Anees
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
>
>
>
>
> *
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>
> *
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>
--
Muhammad Anees
MSc in Economics
The University of Sheffield
United Kingdom
*
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