Analysing spatial point patterns in R - CSIRO

34 Objects, classes and methods in R
> data(humberside)
> plot(humberside)
humberside
Exercise 1 Find out how to modify the command plot(swedishpines) so that the title reads
“Swedish Pines data” and the points are represented by plus-signs instead of circles.
When you type print(swedishpines) or just swedishpines, this invokes the generic commandprint,
which dispatches to the methodprint.ppp, which prints some sensible information
about the point pattern swedishpines at the terminal.
> swedishpines
planar point pattern: 71 points
window: rectangle = [0, 96] x [0, 100] units (one unit = 0.1 metres)
The generic command summary is meant to provide basic summary statistics for a dataset.
When you type summary(swedishpines) this is dispatched to the method summary.ppp, which
computes a sensible set of summary statistics for a point pattern, and prints them at the terminal.
> summary(swedishpines)
Planar point pattern: 71 points
Average intensity 0.0074 points per square unit (one unit = 0.1 metres)
Window: rectangle = [0, 96]x[0, 100]units
Window area = 9600 square units
Unit of length: 0.1 metres
The command density is also generic. It is normally used to compute a kernel density
estimate of a probability distribution from a vector of numbers. (This “default method” is
called density.default.) But there is also a method for point patterns, so that when you type
density(swedishpines), this is dispatched to density.ppp which computes a two-dimensional
kernel estimate of the intensity function.
> plot(density(swedishpines, sigma = 10))
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