These are a bit of a throwback really, and are not very useful - they
are reference degrees of freedom used in computing test statistic and
the p-values, but since the null distributions are non-standard the
reference DoF is not very interpretable.
best,
Simon
On 27/03/2019 13:58, Susan Elias wrote:
Hello Group.
Regarding degrees of freedom in GAM models fit by mgcv, I do understand the
estimated df, but what does "ref.df" in the summary output mean?
I didn't see an explanation in Wood (2017) or find it in the function
code. The answer may be on page 222 of
Wood SN. On p-values for smooth components of an extended generalized
additive model. Biometrika 2013;100(1):221-228
or thereafter, but I am not a statistician. I could use help understanding
what the reference degrees of freedom are.
Thank you,
Susan
--
Simon Wood, School of Mathematics, University of Bristol, BS8 1TW UK
https://people.maths.bris.ac.uk/~sw15190/
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