qknots {DALSM} | R Documentation |
Specification of knots in a cubic P-spline model
Description
Specification of knots for a cubic B-spline basis with K
elements in
a P-spline model. The knots should support the data contained in vector x
and are by default assumed equidistant. Alternatively, they can be based
on the data quantiles. The penalty matrix of the selected penalty order
(3 by default) is also returned.
Usage
qknots(x, xmin = NULL, xmax = NULL, equid.knots = TRUE, pen.order = 3, K = 25)
Arguments
x |
data that the knots should upport. |
xmin |
desired minimum value for the knots. |
xmax |
desired maximum value for the knots. |
equid.knots |
logical indicating if equidistant knots are desired (Default: TRUE). If FALSE, the quantile of |
pen.order |
penalty order if |
K |
number of B-splines in the basis. |
Value
A list containing:
xmin
:
specified minimum value for the knots, except if\min(x) < xmin
, in which case the default value\min(x)-sd(x)
is returned.xmin
:
specified maximum value for the knots, except ifxmax < \max(x)
, in which case the default value\max(x)+sd(x)
is returned.K
:
number of B-splines.knots
:
equidistant knots on (xmin,xmax) ifequidistant.knots
is TRUE, based on quantiles ofx
otherwise.Pd
:
K\times K
penalty matrix of orderpen.order
.pen.order
:
a reminder of the requested penalty order (Default: 3).
Examples
x = runif(500)
obj = qknots(x,xmin=0,xmax=1,K=13)
print(obj)