fourier.Rd
\name{fourier}
\alias{fourier}
\title{
Fourier Basis Function Values
}
\description{
Evaluates a set of Fourier basis functions, or a derivative of these
functions, at a set of arguments.
}
\usage{
fourier(x, nbasis=n, period=span, nderiv=0)
}
\arguments{
\item{x}{
a vector of argument values at which the Fourier basis functions are
to be evaluated.
}
\item{nbasis}{
the number of basis functions in the Fourier basis. The first basis
function is the constant function, followed by sets of sine/cosine
pairs. Normally the number of basis functions will be an odd. The
default number is the number of argument values.
}
\item{period}{
the width of an interval over which all sine/cosine basis functions
repeat themselves. The default is the difference between the largest
and smallest argument values.
}
\item{nderiv}{
the derivative to be evaluated. The derivative must not exceed the
order. The default derivative is 0, meaning that the basis functions
themselves are evaluated.
}
}
\value{
a matrix of function values. The number of rows equals the number of
arguments, and the number of columns equals the number of basis functions.
}
\seealso{
\code{\link{fourierpen}}
}
\examples{
# set up a set of 11 argument values
x <- seq(0,1,0.1)
names(x) <- paste("x", 0:10, sep="")
# compute values for five Fourier basis functions
# with the default period (1) and derivative (0)
(basismat <- fourier(x, 5))
# Create a false Fourier basis, i.e., nbasis = 1
# = a constant function
fourier(x, 1)
}
% docclass is function
\keyword{smooth}