Add Smoothing Spline Modelling Capability to `nlme`

Adds smoothing spline modelling capability to nlme. Fits smoothing spline terms in Gaussian linear and nonlinear mixed-effects models.

lmeSplines

lmeSplines R package (Version: 1.1-14) available on CRAN.

To install from GitHub:

devtools::install_github("agalecki/lmeSplines")

Run example from smspline documentation:

library(lmeSplines)
data(smSplineEx1)

# variable `all` for top level grouping
smSplineEx1$all <- rep(1,nrow(smSplineEx1))
# setup spline Z-matrix
smSplineEx1$Zt <- smspline(~ time, data = smSplineEx1)
fit1s <- lme(y ~ time, data = smSplineEx1,
             random = list(all = pdIdent(~Zt - 1)))
summary(fit1s)