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Analysing spatial point patterns in R - CSIRO

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56 Manipulat<strong>in</strong>g <strong>po<strong>in</strong>t</strong> <strong>patterns</strong><br />

planar <strong>po<strong>in</strong>t</strong> pattern: 3604 <strong>po<strong>in</strong>t</strong>s<br />

w<strong>in</strong>dow: rectangle = [0, 1000] x [0, 500] metres<br />

> bei[1:10]<br />

planar <strong>po<strong>in</strong>t</strong> pattern: 10 <strong>po<strong>in</strong>t</strong>s<br />

w<strong>in</strong>dow: rectangle = [0, 1000] x [0, 500] metres<br />

It is also possible to extract the subset def<strong>in</strong>ed by a <strong>spatial</strong> region. If X is a <strong>po<strong>in</strong>t</strong> pattern<br />

and W is a <strong>spatial</strong> w<strong>in</strong>dow (object of class "ow<strong>in</strong>") then X[W] is the <strong>po<strong>in</strong>t</strong> pattern consist<strong>in</strong>g of<br />

all <strong>po<strong>in</strong>t</strong>s of X that lie <strong>in</strong>side W.<br />

> W W<br />

w<strong>in</strong>dow: rectangle = [100, 800] x [100, 400] units<br />

> bei[W]<br />

planar <strong>po<strong>in</strong>t</strong> pattern: 918 <strong>po<strong>in</strong>t</strong>s<br />

w<strong>in</strong>dow: rectangle = [100, 800] x [100, 400] units<br />

Tip: You may need to put quotes around the subset operator <strong>in</strong> some contexts.<br />

The generic subset operator is [ but the help file is summoned by typ<strong>in</strong>g help("[").<br />

The subset method for <strong>po<strong>in</strong>t</strong> <strong>patterns</strong> is called [.ppp but the help file is summoned<br />

by typ<strong>in</strong>g help("[.ppp").<br />

The command split.ppp allows you to divide a <strong>po<strong>in</strong>t</strong> pattern <strong>in</strong>to sub-<strong>patterns</strong>, and the<br />

command by.ppp allows you to perform an operation on each sub-pattern.<br />

9.2.3 Fiddl<strong>in</strong>g with marks<br />

To extract the marks from a <strong>po<strong>in</strong>t</strong> pattern, use marks:<br />

> m radii X X<br />

Copyright<strong>CSIRO</strong> 2010

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