cbc {cuRe}

Restricted cubic splines with cure

Description

Function for computing the basis matrix for restricted cubic splines which are constant beyond the last knot

Usage

cbc(x, df = NULL, knots = NULL, ortho = FALSE, R.inv = NULL, intercept = FALSE)

Arguments

x

Values to evaluate the basis functions in.

df

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.

knots

Chosen knots for the spline.

ortho

Logical. If TRUE orthogonalization of the basis matrix is carried out.

R.inv

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.

intercept

Logical. If FALSE, the intercept of the restricted cubic spline is removed.

Value

A matrix with containing the basis functions evaluated in x.

References

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.