fasp.object
Function Arrays for Spatial Patterns
A class "fasp"
to represent a
Details
An object of this class is a convenient way of storing (and later plotting, editing, etc) a set of functions $f_{i,j}(r)$ of a real argument $r$, defined for each possible pair $(i,j)$ of indices $1 \le i,j \le n$. We may think of this as a matrix or array of functions $f_{i,j}$.
Function arrays are particularly useful in the analysis of a multitype point pattern (a point pattern in which the points are identified as belonging to separate types). We may want to compute a summary function for the points of type $i$ only, for each of the possible types $i$. This produces a $1 \times m$ array of functions. Alternatively we may compute a summary function for each possible pair of types $(i,j)$. This produces an $m \times m$ array of functions.
For multitype point patterns the command alltypes
will compute arrays of summary functions for each possible
type or for each possible pair of types.
The function alltypes
returns an object of class "fasp"
.
An object of class "fasp"
is a list containing at least the
following components:
[object Object],[object Object],[object Object],[object Object],[object Object]
Functions available
There are methods for plot
, print
and "["
for this class.
The plot method displays the entire array of functions.
The method [.fasp
selects a sub-array using the natural
indices i,j
.
The command eval.fasp
can be used to apply
a transformation to each function in the array,
and to combine two arrays.
See Also
Examples
# multitype point pattern
data(amacrine)
GG <- alltypes(amacrine, "G")
plot(GG)
# select the row corresponding to cells of type "on"
Gon <- GG["on", ]
plot(Gon)
# extract the G function for i = "on", j = "off"
Gonoff <- GG["on", "off", drop=TRUE]
# Fisher variance stabilising transformation
GGfish <- eval.fasp(asin(sqrt(GG)))
plot(GGfish)