Local Linear Regression // A bare-bones implementation of local linear regression, using high-level functions. Can handle both numerical and non-numerical (factor) variables. See Loader (1999) doi:10.1007/b98858, ch2, or Hastie et al (2009) doi:10.1007/978-0-387-84858-7, ch6. The package also contains a scale_df() function which only scales the numeric variables in a dataframe.