ref.df in mgcv gam
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/