Polynomial-spline fit with equally-spaced knots
Spline.fit(Xint, Xvec, Yvec, nKnots = 2, Degree = 3, Wt = 1)a vector of x interval to generate the local linear fit
numeric vectors of data values, Xvec and Yvec must have the same length.
number of equally-spaced knots
degree of polynomial splines
a weight vector or a constant. For longitudinal data, Wt=1/N corresponds to measurement uniform weight and Wt=1/(nni) corresponds subject uniform weight.
Wu, C.O. and Tian, X. Nonparametric Models for Longitudinal Data. Chapman & Hall/CRC. To appear.