Hi Peter,
> On Apr 5, 2019, at 7:22 AM, peter dalgaard <pdalgd at gmail.com>
wrote:
>
> Can't you just check for NA coefficients?
>
>> y <- rnorm(10) ; x <- rep(0,10)
>> coef(lm(y~x))
> (Intercept) x
> -0.0962404 NA
>
> so
>
>> any(is.na(coef(lm(y~x))))
> [1] TRUE
>
> I have a vague recollection that at some point there might have been
dragons lurking in there (? - NA coefs silently removed), but I can't see a
problem with it presently.
I think that the problem you recall related to vcov.lm() and not coef().
vcov.lm() silently removed NAs, which motivated the introduction of the complete
argument, defaulting to TRUE. AFAIK, coef() always included NAs in the
coefficient vector for a singular fit.
Best,
John
-------------------------------------------------
John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
Web: http::/socserv.mcmaster.ca/jfox
>
> -pd
>
>> On 5 Apr 2019, at 12:14 , Witold E Wolski <wewolski at gmail.com>
wrote:
>>
>> lme4 has a function isSingular to check if the fitted model is
Singular,
>>
>> Although lm has the parameter singular.ok = TRUE by defualt, I could
>> not find a function to check if the fitted model is singular.
>>
>> What would be the correct way to implement such a function for and lm
object?
>> Check if df.residuals == 0
>>
>> Thanks
>> Witek
>>
>>
>>
>>
>>
>> --
>> Witold Eryk Wolski
>>
>> ______________________________________________
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>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.