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Spline Interpolation

Syntax

spline(x, y, n=3*length(x), xmin=min(x), xmax=max(x),
        method="fmm")

Arguments

x,y vectors giving the coordinates of the points to be interpolated. Alternatively a single plotting structure can be specified.
n interpolation takes place at n equally spaced points spanning the interval [xmin, xmax].
xmin left-hand endpoint of the interpolation interval.
xmax right-hand endpoint of the interpolation interval.
method this specifies the type of spline to be used. Possible values are "fmm", "natural" and "periodic".

Description

spline performs cubic spline interpolation of the given data points. It returns a list containing components x, and y which give the ordinates where interpolation took place and the interpolated values.

If method="fmm", the spline used is that of Forsythe, Malcolm and Moler (an exact cubic is fitted through the four points at each end of the data, and this is used to determine the end conditions). Natural splines are used when method="natural" and periodic splines when method="periodic".

References

Forsythe, G. E., M. A. Malcolm and C. B. Moler (1977). Computer Methods for Mathematical Computations.

See Also

approx, approxfun, splinefun.

Examples

x <- 1:10 y <- rnorm(10) plot(x, y) lines(spline(x, y))