spatstat.geom (version 3.3-2)

funxy: Spatial Function Class

Description

A simple class of functions of spatial location

Usage

funxy(f, W)

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.

Arguments

f

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

W

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

Author

Adrian Baddeley , Rolf Turner and Ege Rubak .

Details

This command 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.

The result also has a unitname, inherited from W.

See Also

plot.funxy, summary.funxy

Examples

   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])