Ah, thank you very much - I did not understand first brglm was the name of
a package!
Dimitri


On Tue, Oct 1, 2013 at 11:34 AM, Xochitl CORMON
<Xochitl.Cormon@ifremer.fr>wrote:

>
>
>
> <>< <>< <>< <><
>
> Xochitl CORMON
>
> Le 01/10/2013 17:29, Dimitri Liakhovitski a écrit :
>
>> Thank you very much, Bert - it's very helpful.
>> This post says that R issues a warning:
>>
>> Warning message:
>> *glm.fit: fitted probabilities numerically 0 or 1 occurred
>> *
>>
>
> Actually the warning message should be something like:
> glm.fit: algorithm did not converge
>
> The fist warning is not fatal contrary to the second one.. (
> https://stat.ethz.ch/**pipermail/r-help/2012-March/**307352.html<https://stat.ethz.ch/pipermail/r-help/2012-March/307352.html>
> )
>
>
>  However, in my case there is no warning. How could I detect complete
>> separation in my data? I need to be able to flag it in my function.
>>
>
> As said use the separation dectection function: separation.detection{brglm}
>
>  Thank you very much!
>> Dimitri
>>
>>
>>
>> On Tue, Oct 1, 2013 at 10:52 AM, Xochitl CORMON
>> <Xochitl.Cormon@ifremer.fr <mailto:Xochitl.Cormon@**ifremer.fr<Xochitl.Cormon@ifremer.fr>>>
>> wrote:
>>
>>     Hi,
>>
>>     I did have warning messages about convergence issues using binomial
>>     GLM with logit link with my data in the past....
>>
>>     Do you detect separation using the function
>> separation.detection{brglm}?
>>
>>     Regards,
>>
>>     Xochitl C.
>>
>>
>>     <>< <>< <>< <><
>>
>>     Xochitl CORMON
>>     +33 (0)3 21 99 56 84 <tel:%2B33%20%280%293%2021%**2099%2056%2084>
>>
>>
>>     Doctorante en sciences halieutiques
>>     PhD student in fishery sciences
>>
>>     <>< <>< <>< <><
>>
>>     IFREMER
>>     Centre Manche Mer du Nord
>>     150 quai Gambetta
>>     62200 Boulogne-sur-Mer
>>
>>     <>< <>< <>< <><
>>
>>
>>
>>     Le 01/10/2013 16:41, Dimitri Liakhovitski a écrit :
>>
>>         I have this weird data set with 2 predictors and one dependent
>>         variable -
>>         attached.
>>
>>         predictor1 has all zeros except for one 1.
>>         I am runnning a simple logistic regression:
>>
>>         temp<-read.csv("x data for reg224.csv")
>>         myreg<- glm(dv~predictor1+predictor2,_**_data=temp,
>>
>>                        family=binomial("logit"))
>>         myreg$coef2
>>
>>         Everything runs fine and I get the coefficients - and the fact
>>         that there
>>         is only one 1 on one of the predictors doesn't seem to cause any
>>         problems.
>>
>>         However, when I run the same regression in SAS, I get warnings:
>>            Model Convergence Status  Quasi-complete separation of data
>>         points
>>         detected.
>>
>>         Warning: The maximum likelihood estimate may not exist.
>>         Warning: The LOGISTIC procedure continues in spite of the above
>>         warning.
>>         Results shown are based on the last maximum likelihood
>>         iteration. Validity
>>         of the model fit is questionable.
>>
>>         And the coefficients SAS produces are quite different from mine.
>>
>>         I know I'll probably get screamed at because it's not a pure R
>>         question -
>>         but any idea why R is not giving me any warnings in such a
>>         situation?
>>         Does it have no problems with ML estimation in this case?
>>
>>         Thanks a lot!
>>
>>
>>
>>
>>
>>         ______________________________**__________________
>>         R-help@r-project.org <mailto:R-help@r-project.org> mailing list
>>         https://stat.ethz.ch/mailman/_**_listinfo/r-help<https://stat.ethz.ch/mailman/__listinfo/r-help>
>>
>>         <https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
>> >
>>         PLEASE do read the posting guide
>>         http://www.R-project.org/__**posting-guide.html<http://www.R-project.org/__posting-guide.html>
>>
>>         <http://www.R-project.org/**posting-guide.html<http://www.R-project.org/posting-guide.html>
>> >
>>         and provide commented, minimal, self-contained, reproducible code.
>>
>>
>>     ______________________________**__________________
>>     R-help@r-project.org <mailto:R-help@r-project.org> mailing list
>>     https://stat.ethz.ch/mailman/_**_listinfo/r-help<https://stat.ethz.ch/mailman/__listinfo/r-help>
>>
>>     <https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
>> >
>>     PLEASE do read the posting guide
>>     http://www.R-project.org/__**posting-guide.html<http://www.R-project.org/__posting-guide.html>
>>
>>     <http://www.R-project.org/**posting-guide.html<http://www.R-project.org/posting-guide.html>
>> >
>>     and provide commented, minimal, self-contained, reproducible code.
>>
>>
>>
>>
>> --
>> Dimitri Liakhovitski
>>
>


-- 
Dimitri Liakhovitski

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