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Create a Periodic Interpolation Spline

Usage

periodicSpline(obj1, obj2, knots, period, ord)

Arguments

obj1 Either a numeric vector of x values or a formula.
obj2 If obj1 is numeric this should be a numeric vector of the same length. If obj1 is a formula this can be an optional data frame in which to evaluate the names in the formula.
knots An optional numeric vector of knot positions.
period A positive numeric value giving the period for the periodic spline. Defaults to 2 * pi.
ord A positive integer giving the order of the spline. Defaults to 4. See ?splineOrder for a definition of the order of a spline.

Description

Create a periodic interpolation spline, either from x and y vectors, or from a formula/data.frame combination.

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).

Author(s)

Douglas Bates and Bill Venables

See Also

splineKnots, interpSpline, periodic.spline

Examples

xx <- seq( -pi, pi, len = 16 )
yy <- sin( xx )
frm <- data.frame( xx, yy )
pispl <- periodicSpline( xx, yy, period = 2 * pi )
pispl2 <- periodicSpline( yy ~ xx, data = frm, period = 2 * pi )
# pispl and pispl2 should be the same
plot( predict( pispl, seq(-3*pi, 3*pi, len = 101) ) )
plot( pispl )