R-package for interpretable nonparametric modeling of longitudinal data using additive Gaussian processes. Contains functionality for inferring covariate effects and assessing covariate relevances. Various models can be specified using a convenient formula syntax.
Installing from CRAN is probably the easiest option since they might have binaries for your system (so no need to build the package from source yourself).
install.packages('devtools') # if you don't have devtools already devtools::install_github('jtimonen/lgpr', build_vignettes = TRUE)
devtools::install_github('jtimonen/lgpr', ref = "develop")
Github installations are source installations (they require a C++ compiler).