eval.fasp.Rd
\name{eval.fasp}
\alias{eval.fasp}
\title{Evaluate Expression Involving Function Arrays}
\description{
Evaluates any expression involving one or more function arrays
(\code{fasp} objects) and returns another function array.
}
\usage{
eval.fasp(expr, envir, dotonly=TRUE)
}
\arguments{
\item{expr}{
An expression involving the names of objects of class \code{"fasp"}.
}
\item{envir}{
Optional. The environment in which to evaluate the expression,
or a named list containing \code{"fasp"} objects to be used in
the expression.
}
\item{dotonly}{Logical. Passed to \code{\link{eval.fv}}.}
}
\details{
This is a wrapper to make it easier to perform
pointwise calculations with the arrays of summary functions
used in spatial statistics.
A function array (object of class \code{"fasp"}) can be regarded as a matrix
whose entries are functions. Objects of this kind
are returned by the command \code{\link{alltypes}}.
Suppose \code{X} is an object of class \code{"fasp"}.
Then \code{eval.fasp(X+3)} effectively adds 3 to the value of
every function in the array \code{X}, and returns
the resulting object.
Suppose \code{X} and \code{Y} are two objects of class \code{"fasp"}
which are compatible (for example the arrays
must have the same dimensions). Then
\code{eval.fasp(X + Y)} will add the corresponding functions in
each cell of the arrays \code{X} and \code{Y},
and return the resulting array of functions.
Suppose \code{X} is an object of class \code{"fasp"}
and \code{f} is an object of class \code{"fv"}.
Then \code{eval.fasp(X + f)} will add the function \code{f}
to the functions in each cell of the array \code{X},
and return the resulting array of functions.
In general, \code{expr} can be any expression involving
(a) the \emph{names} of objects of class \code{"fasp"} or \code{"fv"},
(b) scalar constants, and (c) functions which are vectorised.
See the Examples.
First \code{eval.fasp} determines which of the \emph{variable names}
in the expression \code{expr} refer to objects of class \code{"fasp"}.
The expression is then evaluated for each cell of the array
using \code{\link{eval.fv}}.
The expression \code{expr} must be vectorised.
There must be at least one object of class \code{"fasp"} in the expression.
All such objects must be compatible.
}
\value{
Another object of class \code{"fasp"}.
}
\seealso{
\code{\link{fasp.object}},
\code{\link{Kest}}
}
\examples{
# manipulating the K function
K <- alltypes(amacrine, "K")
# expressions involving a fasp object
eval.fasp(K + 3)
L <- eval.fasp(sqrt(K/pi))
# expression involving two fasp objects
D <- eval.fasp(K - L)
# subtracting the unmarked K function from the cross-type K functions
K0 <- Kest(unmark(amacrine))
DK <- eval.fasp(K - K0)
## Use of 'envir'
S <- eval.fasp(1-G, list(G=alltypes(amacrine, "G")))
}
\author{\adrian
and \rolf
}
\keyword{spatial}
\keyword{manip}
\keyword{programming}