# pcfdot

##### Multitype pair correlation function (i-to-any)

Calculates an estimate of the multitype pair correlation function
(from points of type `i`

to points of any type)
for a multitype point pattern.

- Keywords
- spatial, nonparametric

##### Usage

`pcfdot(X, i, ...)`

##### Arguments

- X
- The observed point pattern, from which an estimate of the dot-type pair correlation function $g_{i\bullet}(r)$ will be computed. It must be a multitype point pattern (a marked point pattern whose marks are a factor).
- i
- Number or character string identifying the type (mark value)
of the points in
`X`

from which distances are measured. - ...
- Arguments passed to
`pcf.ppp`

.

##### Details

This is a generalisation of the pair correlation function `pcf`

to multitype point patterns.

For two locations $x$ and $y$ separated by a nonzero
distance $r$,
the probability $p(r)$ of finding a point of type $i$ at location
$x$ and a point of any type at location $y$ is
$$p(r) = \lambda_i \lambda g_{i\bullet}(r) \,{\rm d}x \, {\rm d}y$$
where $\lambda$ is the intensity of all points,
and $\lambda_i$ is the intensity of the points
of type $i$.
For a completely random Poisson marked point process,
$p(r) = \lambda_i \lambda$
so $g_{i\bullet}(r) = 1$.
For a stationary multitype point process, the
type-`i`

-to-any-type pair correlation
function between marks $i$ and $j$ is formally defined as
$$g_{i\bullet}(r) = \frac{K_{i\bullet}^\prime(r)}{2\pi r}$$
where $K_{i\bullet}^\prime$ is the derivative of
the type-`i`

-to-any-type $K$ function
$K_{i\bullet}(r)$.
of the point process. See `Kdot`

for information
about $K_{i\bullet}(r)$.

The command `pcfdot`

computes a kernel estimate of
the multitype pair correlation function from points of type $i$
to points of any type.
It uses `pcf.ppp`

to compute kernel estimates
of the pair correlation functions for several unmarked point patterns,
and uses the bilinear properties of second moments to obtain the
multitype pair correlation.

See `pcf.ppp`

for a list of arguments that control
the kernel estimation.

The companion function `pcfcross`

computes the
corresponding analogue of `Kcross`

.

##### Value

- An object of class
`"fv"`

, see`fv.object`

, which can be plotted directly using`plot.fv`

.Essentially a data frame containing columns

r the vector of values of the argument $r$ at which the function $g_{i\bullet}$ has been estimated theo the theoretical value $g_{i\bullet}(r) = 1$ for independent marks. - together with columns named
`"border"`

,`"bord.modif"`

,`"iso"`

and/or`"trans"`

, according to the selected edge corrections. These columns contain estimates of the function $g_{i,j}$ obtained by the edge corrections named.

##### See Also

Mark connection function `markconnect`

.

Multitype pair correlation `pcfcross`

.
Pair correlation `pcf`

,`pcf.ppp`

.
`Kdot`

##### Examples

```
data(amacrine)
p <- pcfdot(amacrine, "on")
p <- pcfdot(amacrine, "on", stoyan=0.1)
plot(p)
```

*Documentation reproduced from package spatstat, version 1.21-0, License: GPL (>= 2)*