ppp.object {spatstat}  R Documentation 
A class "ppp"
to represent a twodimensional point
pattern. Includes information about the window in which the
pattern was observed. Optionally includes marks.
This class represents a twodimensional point pattern dataset. It specifies
If X
is an object of type ppp
,
it contains the following elements:
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.
The internal representation of marks is likely to change in the next release of this package.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner r.turner@auckland.ac.nz
x < runif(100) y < runif(100) X < ppp(x, y, c(0,1),c(0,1)) X ## Not run: plot(X) mar < sample(1:3, 100, replace=TRUE) mm < ppp(x, y, c(0,1), c(0,1), marks=mar) ## Not run: plot(mm) # points with mark equal to 2 ss < mm[ mm$marks == 2 , ] ## Not run: plot(ss) # left half of pattern 'mm' lu < owin(c(0,0.5),c(0,1)) mmleft < mm[ , lu] ## Not run: plot(mmleft) ## Not run: # input data from file qq < scanpp("my.table", unit.square()) # interactively build a point pattern plot(unit.square()) X < as.ppp(locator(10), unit.square()) plot(X) ## End(Not run)