[R] surf.ls

[Peter Dalgaard]

m p <mzp3769 at yahoo.com> writes:

> Hello,
> I am looking into description of surf.ls(spatial)
> and see under value $beta - the coefficients.
> When I use polynomial of degree 2 to fit surface
> I expect to get 4 coefficients:
> 
> z = a_1 x^2 + a_2 xy + a_3 y^2 + a_4
> 
> What do beta really stand for and why do I get
> $beta vector of length 6?

Why do you expect a constant term but no linear terms? I'm too lazy to
verify, but it sounds like that would be your missing 2 coefficients.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907