Description Usage Arguments Details Value Author(s) See Also Examples
Compute the nearest neighbour index map of an object, and return it as a function.
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X |
Any suitable dataset representing a two-dimensional
collection of objects,
such as a point pattern (object of class |
k |
A single integer. The |
... |
Extra arguments are ignored. |
value |
String (partially matched) specifying whether to return the
index of the neighbour ( |
For a collection X of two dimensional objects
(such as a point pattern or a line segment pattern),
the “nearest neighbour index function”
of X is the mathematical function f such that, for any
two-dimensional spatial location (x,y),
the function value f(x,y)
is the index i identifying the closest member of X.
That is, if i = f(x,y) then X[i] is the closest member of
the collection X to the location (x,y).
The command f <- nnfun(X)
returns a function
in the R language, with arguments x,y
, that represents the
nearest neighbour index function of X
. Evaluating the function f
in the form v <- f(x,y)
, where x
and y
are any numeric vectors of equal length containing coordinates of
spatial locations, yields the indices of the nearest neighbours
to these locations.
If the argument k
is specified then the k
-th nearest
neighbour will be found.
The result of f <- nnfun(X)
also belongs to the class
"funxy"
and to the special class "nnfun"
.
It can be printed and plotted immediately as shown in the Examples.
A nnfun
object can be converted to a pixel image
using as.im
.
A function
with arguments x,y
.
The function also belongs to the class "nnfun"
which has
a method for print
.
It also belongs to the class "funxy"
which has methods
for plot
, contour
and persp
.
.
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