# periodicSpline {splines}

### Description

Create a periodic interpolation spline, either from `x`

and `y`

vectors, or from a formula/data.frame combination.

### Usage

periodicSpline(obj1, obj2, knots, period = 2*pi, ord = 4)

### 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
- 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
`splineOrder`

for a definition of the order of a spline.

### Values

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

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) pispl 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" )

Documentation reproduced from R 3.0.2. License: GPL-2.