is.marked.ppp: Test Whether A Point Pattern is Marked
Description
Tests whether a point pattern has ``marks''
attached to the points.
Usage
"is.marked"(X, na.action="warn", ...)
Arguments
X
Point pattern (object of class "ppp")
na.action
String indicating what to do if NA values are
encountered amongst the marks.
Options are "warn", "fatal" and "ignore".
...
Ignored.
Value
Logical value, equal to TRUE if X is a marked point pattern.
Details
``Marks'' are observations attached to each point of a point pattern.
For example the longleaf dataset contains the locations
of trees, each tree being marked by its diameter;
the amacrine dataset gives the locations of cells
of two types (on/off) and the type of cell may be regarded as a mark attached
to the location of the cell.
This function tests whether the point pattern X
contains or involves marked points.
It is a method for the generic function is.marked.
The argument na.action determines what action will be taken
if the point pattern has a vector of marks but some or all of the
marks are NA. Options are "fatal" to cause a fatal
error; "warn" to issue a warning and then return TRUE;
and "ignore" to take no action except returning TRUE.