Linear Interpolation

[ top | up ]

Linear Interpolation

Syntax

approx(x, y, xout, method="linear", n=50, rule=1)
approxfun(x, y, method="linear", rule=1)

Arguments

`x,y`	vectors giving the coordinates of the points to be interpolated. Alternatively a single plotting structure can be specified.
`xout`	an optional set of values specifying where interpolation is to take place.
`method`	this specifies the interpolation method to be used. Currently this is ignored and linear interpolation is always used.
`n`	If `xout is not specified, interpolation takes place at n equally spaced points spanning the interval [min(x),max(x)].`
`rule`	an integer describing how interpolation is to take place outside the interval `[min(x),max(x)]. If rule is 1 then NAs are returned for such points and if it is 2, the value at the closest data extreme is used.`

Description

approx performs linear 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.

approxfun returns a function which will perform linear
interpolation of the given data points.  For a given set of x
values this function will return the corresponding interpolated
values.  This is typically more useful than
approx.
See Also

spline.
Examples
x <- 1:10
y <- rnorm(10)
plot(x, y)
points(approx(x, y))

x <- 1:10
y <- rnorm(10)
f <- approxfun(x, y)
curve(f(x), 0, 10)