
642 Spatial Point Patterns: Methodology and Applications with R
example the nbfires pattern consists of locations of forest fires, marked by 9 different variables.
To classify the fire locations into four groups on the basis of their final fire size:
> NB <- cut(nbfires, "fnl.size", breaks=4)
Note th at setting breaks=4 tells cut to divide (a slight extension of) th e range of the fire sizes into
four roughly equal intervals.
More complex sub divisions can be accomplished using subset.ppp or arithmetic with the
marks:
> big.old <- subset(nbfires, fnl.size > 10 & dis.date < "2001-01-01")
15.2.3 Intensity for point patterns w ith real-valued marks
Suppose