[R] MGCV: Degrees of freedom of smooth terms

[Christoph Scherber]

Dear all,

This is just a quick question regarding degrees of freedom in GAM models fit by MGCV (using select=T):

Can I roughly interpret them as:

1 df: linear effect of x on y
2 df: approximately quadratic of x on y
3 df: approximately cubic effect of x on y?
1 df for a spatial term s(x,y): bilinear effect (?) or how would I call this?

And what does "ref.df" in the summary output mean; is this the unpenalized degrees of freedom for
each term?

Thank you very much for answering!

Best wishes,
Christoph


-- 
PD Dr Christoph Scherber
Georg-August University Goettingen
Department of Crop Science
Agroecology
Grisebachstrasse 6
D-37077 Goettingen
Germany
phone 0049 (0)551 39 8807
fax 0049 (0)551 39 8806
http://www.gwdg.de/~cscherb1