Laurent 14 juin 12:02 afficher les options
De : "Laurent" <eddy_l... at hotmail.com> - Rechercher les
messages de cet
auteur
Date : Tue, 14 Jun 2005 03:02:37 -0700
Local : Mar 14 juin 2005 12:02
Objet : bs() function of the splines package
R??pondre | R??pondre ?? l'auteur | Transf??rer | Imprimer | Message
individuel
| Afficher l'original | Retirer | Signaler un cas d'utilisation abusive
Hello,
I'm implementing a function using non uniform B-Splines. Looking at the
code of the bs() function, I realized that if the intercept was set to
TRUE, the behavior of the function was the following (df is the number
of degrees of freedom that I believe can be interpreted as the number
of control points):
- Compute df- ord + 1 _internal_ knots (ord is the order of the spline)
- Add ord times the boundaries values at each extrem of the knots
vector.
- Compute the design matrix on this vector.
This results in a design matrix with df+1 columns. The bs function then
_removes_ the first column of the matrix (resulting as expected in a
matrix with df columns).
I'm a bit confused, does anyone see a mathematical justification to
this manipulation?
In this case, is it licit tu use df- ord + 2 internal knots and remove
the last columns too?
Thanks a lot,
Laurent
