Analysing spatial point patterns in R - CSIRO
Analysing spatial point patterns in R - CSIRO
Analysing spatial point patterns in R - CSIRO
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187<br />
31 Exploratory tools for multitype <strong>po<strong>in</strong>t</strong> <strong>patterns</strong><br />
This section covers some tools for exploratory data analysis of multitype <strong>po<strong>in</strong>t</strong> <strong>patterns</strong> (i.e.<br />
where the marks are categorical).<br />
31.1 Intensity<br />
The Lans<strong>in</strong>g Woods data give the locations of 6 species of trees <strong>in</strong> a forest <strong>in</strong> Michigan. Elementary<br />
estimates of the frequency distribution of species, and the <strong>in</strong>tensity of each species, are<br />
available from summary.ppp.<br />
> data(lans<strong>in</strong>g)<br />
> summary(lans<strong>in</strong>g)<br />
Marked planar <strong>po<strong>in</strong>t</strong> pattern: 2251 <strong>po<strong>in</strong>t</strong>s<br />
Average <strong>in</strong>tensity 2250 <strong>po<strong>in</strong>t</strong>s per square unit (one unit = 924 feet)<br />
*Pattern conta<strong>in</strong>s duplicated <strong>po<strong>in</strong>t</strong>s*<br />
Multitype:<br />
frequency proportion <strong>in</strong>tensity<br />
blackoak 135 0.0600 135<br />
hickory 703 0.3120 703<br />
maple 514 0.2280 514<br />
misc 105 0.0466 105<br />
redoak 346 0.1540 346<br />
whiteoak 448 0.1990 448<br />
W<strong>in</strong>dow: rectangle = [0, 1]x[0, 1]units<br />
W<strong>in</strong>dow area = 1 square unit<br />
Unit of length: 924 feet<br />
It’s sensible to exam<strong>in</strong>e the sub-<strong>patterns</strong> of different types separately, us<strong>in</strong>g split.ppp.<br />
> plot(split(lans<strong>in</strong>g))<br />
Copyright<strong>CSIRO</strong> 2010