Copied from [select_knots](https://rdrr.io/cran/refund/src/R/select_knots.R) because the original is not exported for use.
select_knots(t, knots = 10, p = 3, option = "equally-spaced")
Numeric
Numeric scalar or vector, the number/numbers of knots or the vector/vectors of knots for each dimension. Default = 10
Numeric, the degrees of B-splines. Default = 3.
Character, knot spacing, can be `"equally-spaced"` or `"quantile"`