You need a space between power and -1
Check the help for glm
Tony
Peter A. Lachenbruch
Department of Public Health
Oregon State University
Corvallis, OR 97330
Phone: 541-737-3832
FAX: 541-737-4001
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of roland
andersson
Sent: Wednesday, November 05, 2008 10:54 PM
To: [email protected]
Subject: Re: st: Interpretation of regressionmodel of ln-transformed
variable
I tried the model
xi: glm lengthof stay lapscopy i.appdgn2 i.alderk prepermalign
precardioscleros preperdiabetes cons, eform link(power-1) nocons
and get an error message "unrecognized command: power"
Roland
2008/11/5 Nick Cox <[email protected]>:
> I doubt that anything is wrong with Tony's model except that
> -eform("exp(b)")- should just be -eform-.
>
> Nick
>
> roland andersson
>
> Peter and Maarten
>
> I am sorry Peter. Your model is not accepted by Stata. I tried
> different alternativ without success.
>
> However I tried Maarten GLM model
>
> xi: glm studytime i.drug c_age cons, family(gaussian) link(log) nocons
> eform
>
> on my data and got a different result compared to the regress of the
> lnLOS. Now laparoscopy has shorter LOS. Which method is correct?
>
>
> 2008/11/5 Lachenbruch, Peter <[email protected]>:
>
>> The issue seems to be that hospitals have a closure date on stay when
>> you are doing a study after patients are certain (or almost certain)
> to
>> have been discharged (e.g., all records are from admissions at least
a
>> year old).
>>
>> An alternative model might fit the reciprocal of the mean rather than
>> the log of the observations (thus obviating problems with 0 days of
> stay
>> - e.g. an outpatient visit to the ER) in this case you could use
>> generalized linear models to get
>> xi: glm LOS lapscopic i.appdgn age agesq cons, eform("exp(b)")
>> link(power -1) nocons
>>
>>
>> Tony
>
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