Function for computing the basis matrix for restricted cubic splines which are constant beyond the last knot
cbc(x, df = NULL, knots = NULL, ortho = FALSE, R.inv = NULL, intercept = FALSE)
A matrix with containing the basis functions evaluated in x
.
Values to evaluate the basis functions in.
Degrees of freedom. One can supply df
rather than knots; cbc
then chooses df + 1
knots
at suitably chosen quantiles of x
(which will ignore missing values) and adds an additional knot at the 95th
quantile of x
.
Chosen knots for the spline.
Logical. If TRUE
orthogonalization of the basis matrix is carried out.
Matrix or vector containing the values of the R matrix from the QR decomposition of the basis matrix.
This is used for making new predictions based on the initial orthogonalization.
Therefore the default is NULL
.
Logical. If FALSE
, the intercept of the restricted cubic spline is removed.
Andersson T.M.-L., et al. (2011) Estimating and modelling cure in population-based cancer studies within the framework of flexible parametric survival models. BMC Medical Research Methodology, 11:96.