This class represents
a two-dimensional point pattern dataset. It specifies
- the locations of the points
- the window in which the pattern was observed
- optionally, a ``mark'' attached to each point
(extra information such as a type label).
If X is an object of type ppp,
it contains the following elements:
ll{
x vector of $x$ coordinates of data points
y vector of $y$ coordinates of data points
n number of points
window window of observation
(an object of class owin)
marks optional vector of marks
}
Users are strongly advised not to manipulate these entries
directly.
Objects of class "ppp"
may be created by the function
ppp
and converted from other types of data by the function
as.ppp.
Note that you must always specify the window of observation;
there is intentionally no default action of ``guessing'' the window
dimensions from the data points alone. Standard point pattern datasets provided with the package
include
amacrine,
betacells,
bramblecanes,
cells,
demopat,
ganglia,
lansing,
longleaf,
nztrees,
redwood,
simdat and
swedishpines.
Use data(xxx) to access the dataset xxx.
Point patterns may be scanned from your own data files by
scanpp or by using read.table and
as.ppp.
They may be manipulated by the functions
subset.ppp,
[.ppp and
superimpose.
Point pattern objects can be plotted just by typing plot(X)
which invokes the plot method for point pattern objects,
plot.ppp. See plot.ppp for further information.
There are also methods for summary and print
for point patterns. Use summary(X) to see a useful description
of the data.
Patterns may be generated at random by
runifpoint,
rpoispp,
rMaternI,
rMaternII,
rSSI,
rNeymanScott,
rMatClust,
and
rThomas.
Most functions which are intended to operate on a window
(of class owin)
will, if presented with a ppp object instead,
automatically extract the window information from the point pattern.