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Analysing spatial point patterns in R - CSIRO

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0.005<br />

4.6 Exploratory data analysis 23<br />

where 10 is my chosen value for the standard deviation of the Gaussian smooth<strong>in</strong>g kernel: it is<br />

10 decimetres, i.e. one metre. If you prefer a contour plot,<br />

> contour(density(X, 10), axes = FALSE)<br />

density(X, 10)<br />

0.004<br />

0.006<br />

0.005<br />

0.005<br />

0.011<br />

0.006<br />

0.01<br />

0.009<br />

0.008<br />

0.009<br />

0.01<br />

0.007<br />

0.008<br />

0.009<br />

0.007<br />

0.009<br />

0.01<br />

0.004<br />

0.003<br />

0.007<br />

0.009<br />

0.01<br />

0.006<br />

0.011<br />

0.013<br />

0.005<br />

0.015<br />

0.004<br />

0.012<br />

0.014<br />

The contours are labelled <strong>in</strong> density units of “trees per square decimetre”.<br />

4.6 Exploratory data analysis<br />

Spatstat is designed to support all the standard types of exploratory data analysis for <strong>po<strong>in</strong>t</strong><br />

<strong>patterns</strong>.<br />

One common example is quadrat count<strong>in</strong>g. The study region is divided <strong>in</strong>to rectangles<br />

(‘quadrats’) of equal size, and the number of <strong>po<strong>in</strong>t</strong>s <strong>in</strong> each rectangle is counted.<br />

> Q Q<br />

x<br />

y [0,24] (24,48] (48,72] (72,96]<br />

(66.7,100] 7 3 6 5<br />

(33.3,66.7] 5 9 7 7<br />

[0,33.3] 4 3 6 9<br />

> plot(X)<br />

> plot(Q, add = TRUE, cex = 2)<br />

Copyright<strong>CSIRO</strong> 2010

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