linearKcross
Multitype K Function (Cross-type) for Linear Point Pattern
For a multitype point pattern on a linear network, estimate the multitype $K$ function which counts the expected number of points of type $j$ within a given distance of a point of type $i$.
- Keywords
- spatial, nonparametric
Usage
linearKcross(X, i, j, r=NULL, ..., correction="Ang")Arguments
- X
- The observed point pattern,
from which an estimate of the cross type $K$ function
$K_{ij}(r)$ will be computed.
An object of class
"lpp"which must be a multitype point pattern (a marked point pattern whose marks are a f - i
- Number or character string identifying the type (mark value)
of the points in
Xfrom which distances are measured. Defaults to the first level ofmarks(X). - j
- Number or character string identifying the type (mark value)
of the points in
Xto which distances are measured. Defaults to the second level ofmarks(X). - r
- numeric vector. The values of the argument $r$ at which the $K$-function $K_{ij}(r)$ should be evaluated. There is a sensible default. First-time users are strongly advised not to specify this argument. See below for important conditio
- correction
- Geometry correction.
Either
"none"or"Ang". See Details. - ...
- Ignored.
Details
This is a counterpart of the function Kcross
for a point pattern on a linear network (object of class "lpp").
The arguments i and j will be interpreted as
levels of the factor marks(X).
If i and j are missing, they default to the first
and second level of the marks factor, respectively.
The argument r is the vector of values for the
distance $r$ at which $K_{ij}(r)$ should be evaluated.
The values of $r$ must be increasing nonnegative numbers
and the maximum $r$ value must not exceed the radius of the
largest disc contained in the window.
Value
- An object of class
"fv"(seefv.object).
Warnings
The arguments i and j are interpreted as
levels of the factor marks(X). Beware of the usual
trap with factors: numerical values are not
interpreted in the same way as character values.
References
Baddeley, A, Jammalamadaka, A. and Nair, G. (to appear) Multitype point process analysis of spines on the dendrite network of a neuron. Applied Statistics (Journal of the Royal Statistical Society, Series C), In press.
See Also
Examples
data(chicago)
K <- linearKcross(chicago, "assault", "robbery")