predict.bSpline: Evaluate a Spline at New Values of x

Description Usage Arguments Value Author(s) See Also Examples

Description

The predict methods for the classes that inherit from the virtual classes bSpline and polySpline are used to evaluate the spline or its derivatives. The plot method for a spline object first evaluates predict with the x argument missing, then plots the resulting xyVector with type = "l".

Usage

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## S3 method for class 'bSpline'
predict(object, x, nseg = 50, deriv = 0, ...)
## S3 method for class 'nbSpline'
predict(object, x, nseg = 50, deriv = 0, ...)
## S3 method for class 'pbSpline'
predict(object, x, nseg = 50, deriv = 0, ...)
## S3 method for class 'npolySpline'
predict(object, x, nseg = 50, deriv = 0, ...)
## S3 method for class 'ppolySpline'
predict(object, x, nseg = 50, deriv = 0, ...)

Arguments

object

An object that inherits from the bSpline or the polySpline class.

x

A numeric vector of x values at which to evaluate the spline. If this argument is missing a suitable set of x values is generated as a sequence of nseq segments spanning the range of the knots.

nseg

A positive integer giving the number of segments in a set of equally-spaced x values spanning the range of the knots in object. This value is only used if x is missing.

deriv

An integer between 0 and splineOrder(object) - 1 specifying the derivative to evaluate.

...

further arguments passed to or from other methods.

Value

an xyVector with components

x

the supplied or inferred numeric vector of x values

y

the value of the spline (or its deriv'th derivative) at the x vector

Author(s)

Douglas Bates and Bill Venables

See Also

xyVector, interpSpline, periodicSpline

Examples

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require(graphics); require(stats)
ispl <- interpSpline( weight ~ height,  women )
opar <- par(mfrow = c(2, 2), las = 1)
plot(predict(ispl, nseg = 201),     # plots over the range of the knots
     main = "Original data with interpolating spline", type = "l",
     xlab = "height", ylab = "weight")
points(women$height, women$weight, col = 4)
plot(predict(ispl, nseg = 201, deriv = 1),
     main = "First derivative of interpolating spline", type = "l",
     xlab = "height", ylab = "weight")
plot(predict(ispl, nseg = 201, deriv = 2),
     main = "Second derivative of interpolating spline", type = "l",
     xlab = "height", ylab = "weight")
plot(predict(ispl, nseg = 401, deriv = 3),
     main = "Third derivative of interpolating spline", type = "l",
     xlab = "height", ylab = "weight")
par(opar)