Analysing spatial point patterns in R - CSIRO

10.3 Manipulating images 69
0 200 600 1000
hickory
400 800 1200 1600
0 200 600 1000
maple
redoak
400 800 1200 1600 100 300 500
100 300 500
This command divided the Lansing Woods point pattern dataset into 6 sub-patterns of
different tree species, extracted the 3 most common species, computed the kernel smoothed
intensity estimate for each species, and then displayed scatterplots of the intensity estimates for
each pair of species. The plot suggests that hickory and maple trees are strongly segregated
from one another (since a high density of hickories is strongly associated with a low density of
maples).
10.3 Manipulating images
10.3.1 Subsets of an image
The subset operator [ has a method for pixel images, [.im:
> X[S]
> X[S, drop = TRUE]
The subset to be extracted is determined by the index argument S.
If S is a point pattern, or a list(x,y), then the values of the pixel image X at these points
are extracted, and returned as a vector.
If S is a window (an object of class "owin"), the values of the image inside this window
are extracted. The result is a pixel image if possible, and a numeric vector otherwise (see
help("[.im") for details).
CopyrightCSIRO 2010