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Analysing spatial point patterns in R - CSIRO

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176 Validation of fitted Gibbs models<br />

qqplot.ppm(fit, nsim=39)<br />

data quantile<br />

−50 0 50 100<br />

−100 −50 0 50 100<br />

Mean quantile of simulations<br />

This shows a Q–Q plot of the smoothed residuals, with <strong>po<strong>in</strong>t</strong>wise 5% critical envelopes from<br />

simulations of the fitted model. This suggests that the Strauss model is reasonable.<br />

These validation techniques generalise and unify many exist<strong>in</strong>g exploratory methods. For<br />

particular models of <strong>in</strong>ter<strong>po<strong>in</strong>t</strong> <strong>in</strong>teraction, the Q–Q plot is closely related to the summary<br />

functions F, G and K. See [12].<br />

28.3 New methods<br />

Several new diagnostic tools for validat<strong>in</strong>g the <strong>in</strong>teraction term <strong>in</strong> a <strong>po<strong>in</strong>t</strong> process model will be<br />

published soon [8]. These methods will then be released <strong>in</strong> spatstat.<br />

Copyright<strong>CSIRO</strong> 2010

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