Internal Function
bw_rot(y_data, x_data, y_grid, x, p, q, mu, nu, kernel_type, regularize)
bandwidth sequence
Numeric matrix/data frame, the raw data of independent.
Numeric matrix/data frame, the raw data of covariates.
Numeric vector, the evaluation points.
Numeric, specifies the evaluation point(s) in the x-direction.
Integer, polynomial order.
Integer, polynomial order.
Integer, order of derivative.
Integer, order of derivative.
String, the kernel.
Boolean.