# funxy

##### Spatial Function Class

A simple class of functions of spatial location

##### Usage

`funxy(f, W)`

##### 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.

##### 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`

.

##### 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`

.

##### See Also

##### Examples

```
# 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])
# }
```

*Documentation reproduced from package spatstat, version 1.64-1, License: GPL (>= 2)*