basis  R Documentation 
Compute a basis for a natural cubic spline, by default using the parameterisation described by Royston and Parmar (2002). Used for flexible parametric survival models.
basis(knots, x, spline = "rp")
knots 
Vector of knot locations in increasing order, including the boundary knots at the beginning and end. 
x 
Vector of ordinates to compute the basis for. 
spline 

The exact formula for the basis is given in flexsurvspline
.
A matrix with one row for each ordinate and one column for each knot.
basis
returns the basis, and dbasis
returns its derivative
with respect to x
.
fss
and dfss
are the same, but with the order of the
arguments swapped around for consistency with similar functions in other R
packages.
Christopher Jackson <chris.jackson@mrcbsu.cam.ac.uk>
Royston, P. and Parmar, M. (2002). Flexible parametric proportionalhazards and proportionalodds models for censored survival data, with application to prognostic modelling and estimation of treatment effects. Statistics in Medicine 21(1):21752197.
Wang W, Yan J (2021). ShapeRestricted Regression Splines with R Package splines2. Journal of Data Science, 19(3), 498517.
flexsurvspline
.
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