funxy: Spatial Function Class

Description

A simple class of functions of spatial location

Usage

funxy(f, W)

Arguments

A function in the R language with arguments x,y (at least)

Window (object of class "owin") inside which the function is well-defined.

Value

A function with the same arguments as f, which also belongs to the class "funxy". This class has methods for print, plot, contour and persp.

Details

This creates an object of class "funxy". This is a simple mechanism for handling a function of spatial location \(f(x,y)\) to make it easier to display and manipulate.

f should be a function in the R language. The first two arguments of f must be named x and y respectively.

W should be a window (object of class "owin") inside which the function f is well-defined.

The function f should be vectorised: that is, if x and y are numeric vectors of the same length n, then v <- f(x,y) should be a vector of length n.

The resulting function g <- funxy(f, W) has the same formal arguments as f and can be called in the same way, v <- g(x,y) where x and y are numeric vectors. However it can also be called as v <- g(X), where X is a point pattern (object of class "ppp" or "lpp") or a quadrature scheme (class "quad"); the function will be evaluated at the points of X.

Examples

Run this code

# NOT RUN {
   f <- function(x,y) { x^2 + y^2 - 1} 
   g <- funxy(f, square(2))
   g
   ## evaluate function at any x, y coordinates
   g(0.2, 0.3)
   ## evaluate function at the points of a point pattern
   g(cells[1:4])
# }