[R-sig-ME] how to get satterthwaite/Kenward-Roger degrees of freedom for heterogeneous-variance one-way ANOVA from an object of nlme::gls

[Qiu, Weiliang /US]

Greetings. I am using nlme::gls() to perform heterogeneous-variance one-way ANOVA and would like to get type III anova table. It looks like nlme:::anova.gls() does not provide Satterthwaite or Kenward-Roger degree of freedom. Please see below an example.


library(nlme)

res.gls <- nlme::gls(extra ~ group, data = sleep, weights = varIdent(form = ~1|group))

nlme:::anova.gls(res.gls, type = "marginal")


Could you suggest how to get type III anova table with Satterthwaite/Kenward-Roger degree of freedom from an object of nlme::gls()? Thanks!

Best regards,

Weiliang

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