Visit each point in a point pattern, find the neighbouring points, and summarise their marks

`markstat(X, fun, N=NULL, R=NULL, …)`

X

A marked point pattern.
An object of class `"ppp"`

.

fun

Function to be applied to the vector of marks.

N

Integer. If this argument is present,
the neighbourhood of a point of `X`

is defined to consist of the
`N`

points of `X`

which are closest to it.

R

Nonnegative numeric value. If this argument is present,
the neighbourhood of a point of `X`

is defined to consist of
all points of `X`

which lie within a distance `R`

of it.

…

extra arguments passed to the function `fun`

.
They must be given in the form `name=value`

.

Similar to the result of `apply`

.
if each call to `fun`

returns a single numeric value,
the result is a vector of dimension `npoints(X)`

, the number of points
in `X`

.
If each call to `fun`

returns a vector of the same length
`m`

, then the result is a matrix of dimensions `c(m,n)`

;
note the transposition of the indices, as usual for the family of
`apply`

functions.
If the calls to `fun`

return vectors of different lengths,
the result is a list of length `npoints(X)`

.

This algorithm visits each point in the point pattern `X`

,
determines which points of `X`

are ``neighbours'' of the current
point, extracts the marks of these neighbouring points,
applies the function `fun`

to the marks,
and collects the value or values returned by `fun`

.

The definition of ``neighbours'' depends on the arguments
`N`

and `R`

, exactly one of which must be given.

If `N`

is given, then the neighbours of the current
point are the `N`

points of `X`

which are closest to
the current point (including the current point itself).
If `R`

is given, then the neighbourhood of the current point
consists of all points of `X`

which lie closer than a distance `R`

from the current point.

Each point of `X`

is visited; the neighbourhood
of the current point is determined; the marks of these points
are extracted as a vector `v`

; then the function
`fun`

is called as:

`fun(v, …)`

where `…`

are the arguments passed from the call to
`markstat`

.

The results of each call to `fun`

are collected and returned
according to the usual rules for `apply`

and its
relatives. See the section on **Value**.

This function is just a convenient wrapper for a common use of the
function `applynbd`

. For more complex tasks,
use `applynbd`

.
To simply tabulate the marks in every `R`

-neighbourhood, use
`marktable`

.

# NOT RUN { trees <- longleaf # } # NOT RUN { # average diameter of 5 closest neighbours of each tree md <- markstat(trees, mean, N=5) # range of diameters of trees within 10 metre radius rd <- markstat(trees, range, R=10) # }