[R] glm error message when using family Gamma(link="inverse")

[Prof Brian Ripley]

On Tue, 9 Dec 2008, John Sorkin wrote:

> R 2.5

Please

1) do as the posting guide asks, and quote version numbers accurately.
2) do as the posting guide asks, and update *before* posting.

That's too old a version to support here.

> windows XP
>
> I am getting an error from glm() that I don't understand. Any help or suggestions would be appreciated. N.B. 1<=AAMTCAREJ<=327900
>
>> summary(data$AAMTCAREJ)
>    Min.  1st Qu.   Median     Mean  3rd Qu.     Max.
>     1.0    404.3   1430.0   6567.0   5457.0 327900.0
>
>
>> fitglm<-glm(AAMTCAREJ~sexcat+H_AGE+SmokeCat+InsuranceCat+MedicadeCat+
> + incomegrp+racecat+MARSTATJS+EdCat+bmiNewjohn,data=data,family=Gamma(link = "inverse"))
> Error: no valid set of coefficients has been found: please supply starting values
> In addition: Warning message:
> NaNs produced in: log(x)

That model is not necessarily valid: the linear predictor has to be 
strictly positive.  If you really know why it is applicable you will be 
able to give starting values (e.g. maybe all the columns of the design 
matrix are positive, in which case you will be able to find suitable 
positive initial coefficients).

> Thanks
> John
>
> John David Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
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