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cobs (version 1.3-2)

qbsks2: Quantile B-Spline with Fixed Knots

Description

Compute B-spline coefficients for regression quantile B-spline with stepwise knots selection and quantile B-spline with fixed knots regression spline, using Ng (1996)'s algorithm.

Usage

qbsks2(x,y,w,pw, knots,nknots, degree,Tlambda, constraint, ptConstr, maxiter, trace, nrq,nl1, neqc, tau, select.lambda, ks, do.select, knots.add, repeat.delete.add, ic, print.mesg, give.pseudo.x = TRUE, rq.tol = 1e-8, tol.kn = 1e-6, tol.0res = 1e-6, print.warn, nk.start)

Arguments

x
numeric vector, sorted increasingly, the abscissa values
y
numeric, same length as x, the observations.
w
numeric vector of weights, same length as x, as in cobs.
pw
penalty weights vector ... ...
knots
numeric vector of knots of which nknots will be used.
nknots
number of knots to be used.
degree
integer specifying polynomial degree; must be 1 or 2.
Tlambda
(vector of) smoothing parameter(s) $\lambda$, see drqssbc2.
constraint
string (or empty) specifying the global constraints; see cobs.
ptConstr
list of pointwise constraints.
maxiter
non-negative integer: maximal number of iterations, passed to drqssbc2.
trace
integer or logical indicating the tracing level of the underlying algorithms; not implemented (due to lack of trace in quantreg ...)
nrq,nl1,neqc
integers specifying dimensionalities, directly passed to drqssbc2, see there.
tau
desired quantile level (in interval $(0,1)$).
select.lambda
passed to drqssbc2, see there.
ks
number used as offset in SIC/AIC/BIC.
do.select
logical indicating if knots shall be selected (instead of used as specified).
knots.add, repeat.delete.add
logicals, see cobs.
ic
information criterion to use, see cobs.
print.mesg
an integer indicating how qbsks2() should print message about its current stages.
give.pseudo.x
logical indicating if the pseudo design matrix $X\~$ should be returned (as sparse matrix).
rq.tol
numeric convergence tolerance for the interior point algorithm called from rq.fit.sfnc() or rq.fit.sfn().
tol.kn
“tolerance” for shifting the outer knots.
tol.0res
tolerance passed to drqssbc2.
print.warn
flag indicating if and how much warnings and information is to be printed; currently just passed to drqssbc2.
nk.start
number of starting knots used in automatic knot selection.

Value

a list with components

Details

This is an auxiliary function for cobs(*, lambda = 0), possibly interesting on its own. This documentation is currently sparse; read the source code!

References

Ng, P. (1996) An Algorithm for Quantile Smoothing Splines, Computational Statistics \& Data Analysis 22, 99--118.

See also the references in cobs.

See Also

the main function cobs; further drqssbc2 which is called from qbsks2().