periodicSpline
Create a Periodic Interpolation Spline
Create a periodic interpolation spline, either from x and
y vectors, or from a formula/data.frame combination.
- Keywords
- models
Usage
periodicSpline(obj1, obj2, knots, period = 2*pi, ord = 4L)Arguments
- obj1
either a numeric vector of
xvalues or a formula.- obj2
if
obj1is numeric this should be a numeric vector of the same length. Ifobj1is a formula this can be an optional data frame in which to evaluate the names in the formula.- knots
optional numeric vector of knot positions.
- period
positive numeric value giving the period for the periodic spline. Defaults to
2 * pi.- ord
integer giving the order of the spline, at least 2. Defaults to 4. See
splineOrderfor a definition of the order of a spline.
Value
An object that inherits from class spline. The object can be in
the B-spline representation, in which case it will be a
pbSpline object, or in the piecewise polynomial representation
(a ppolySpline object).
See Also
Examples
library(splines)
# NOT RUN {
require(graphics); require(stats)
xx <- seq( -pi, pi, length.out = 16 )[-1]
yy <- sin( xx )
frm <- data.frame( xx, yy )
pispl <- periodicSpline( xx, yy, period = 2 * pi)
# }
# NOT RUN {
pispl
# }
# NOT RUN {
pispl2 <- periodicSpline( yy ~ xx, frm, period = 2 * pi )
stopifnot(all.equal(pispl, pispl2)) # pispl and pispl2 are the same
plot( pispl ) # displays over one period
points( yy ~ xx, col = "brown")
plot( predict( pispl, seq(-3*pi, 3*pi, length.out = 101) ), type = "l" )
# }