subset.ppp {spatstat} | R Documentation |
Extract a subset of a point pattern, either by thinning the points or by trimming the window.
subset.ppp(x, subset, window, drop, ...) subset.ppp(x, subset, window) x[subset] x[subset,window]
x |
A two-dimensional point pattern.
An object of class "ppp" .
|
subset |
logical vector indicating which points should be retained. |
window |
window (an object of class "owin" )
delineating a subset of the original observation window.
|
drop |
Ignored - this argument is required for consistency with other
methods for "[" .
|
... |
Ignored - this argument is required for consistency with other
methods for "[" .
|
This function takes performs either ``thinning'' (retaining/deleting some points of a point pattern) or ``trimming'' (reducing the window of observation to a smaller subregion and retaining only those points which lie in the subregion).
The pattern will be ``thinned''
if subset
is specified. This should
be a logical vector of length equal to the number of points in the
point pattern x
.
The points (x$x[i], x$y[i])
for which
subset[i]=TRUE
will be retained, and the others
will be deleted.
The pattern will be ``trimmed''
if window
is specified. This should
be an object of class owin
specifying a window of observation
to which the point pattern x
will be
trimmed. The points of x
lying inside the new
window
will be retained.
Both ``thinning'' and ``trimming'' can be performed together.
Use the function unmark
to remove marks from a
marked point pattern.
A point pattern (of class "ppp"
).
The function does not check whether window
is a subset of
x$window
.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf
ppp.object
,
owin.object
,
unmark
library(spatstat) data(longleaf) # Longleaf pines data plot(longleaf) # adult trees defined to have diameter at least 30 cm adult <- (longleaf$marks >= 30) longadult <- longleaf[adult] # equivalent to: longadult <- subset.ppp(longleaf, subset=adult) plot(longadult) # note that the marks are still retained. # Use unmark(longadult) to remove the marks # New Zealand trees data data(nztrees) plot(nztrees) # plot shows a line of trees at the far right abline(v=148, lty=2) # cut along this line nzw <- owin(c(0,148),c(0,95)) # the subwindow # trim dataset to this subwindow nzsub <- nztrees[,nzw] # equivalent to: nzsub <- subset.ppp(nztrees, window=nzw) plot(nzsub) # Redwood data data(redwood) plot(redwood) # Random thinning: delete 60% of data retain <- (runif(redwood$n) < 0.4) thinred <- redwood[retain] plot(thinred) # Lansing woods data - multitype points data(lansing) # hickory trees only hick <- lansing[lansing$marks == "hickory", ] # still a marked pattern -- remove marks hick <- unmark(hick)