knots.dierckx: Extract the knots from a dierckx object
In DierckxSpline: R companion to "Curve and Surface Fitting with Splines"

Description Usage Arguments Details Value Author(s) References See Also Examples

Extract either all or only the interior knots from an object of class dierckx.

1 2	## S3 method for class 'dierckx' knots(Fn, interior=TRUE, ...)

Fn

an object of class dierckx

interior

logical:

if TRUE, the first Fn[["k"]]+1 of Fn[["knots"]] are dropped, and the next Fn[["g"]] are returned.

Otherwise, the first Fn[["n"]] of Fn[["knots"]] are returned.

...

ignored

The knots component of at least some dierckx objects is of length Fn[["nest"]], but only the first Fn[["n"]] of them are actually used. Moreover, the first and last Fn[["k"]]+1 of them are end knots while the remaining Fn[["g"]] are interior knots.

Numeric vector. If 'interior' is TRUE, this vector has length = Fn[["g"]]. Otherwise, it has length Fn[["n"]].

Sundar Dorai-Raj

Dierckx, P. (1991) Curve and Surface Fitting with Splines, Oxford Science Publications.

curfit, concon, spline, smooth.spline

x <- 0:24
y <- c(1.0,1.0,1.4,1.1,1.0,1.0,4.0,9.0,13.0,
       13.4,12.8,13.1,13.0,14.0,13.0,13.5,
       10.0,2.0,3.0,2.5,2.5,2.5,3.0,4.0,3.5)

z1 <- curfit(x, y, method = "ss", s = 0, k = 3)

knots(z1)
knots(z1, interior=FALSE) # to see all knots