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multivariate poisson hidden markov models for analysis of spatial ...

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model, as indicated by the loglikelihood values, increases significantly. Figure 6.12<br />

indeed illustrates that the loglikelihood <strong>of</strong> the independence and the common covariance<br />

<strong>models</strong> is higher than the loglikelihoods <strong>of</strong> the restricted covariance model over the<br />

range <strong>of</strong> component solutions ( k =1 to 7). Figure 6.13 illustrates that the loglikelihood<br />

<strong>of</strong> the independence model is higher than the loglikelihoods <strong>of</strong> the restricted and the<br />

common covariance model over the range <strong>of</strong> component solutions ( k =1 to 7) <strong>for</strong> the<br />

<strong>hidden</strong> Markov <strong>models</strong>.<br />

-575<br />

-675<br />

Loglikelihood<br />

-775<br />

-875<br />

-975<br />

-1075<br />

-1175<br />

1 2 3 4 5 6 7<br />

k ( the Number <strong>of</strong> States)<br />

restricted covariance common covariance independence<br />

Figure 6.13: Loglikelihood against the number <strong>of</strong> components ( k ) <strong>for</strong> the <strong>multivariate</strong><br />

Poisson <strong>hidden</strong> Markov <strong>models</strong><br />

From the viewpoint <strong>of</strong> model fit, Figure 6.13 this partly justifies the use <strong>of</strong> the model<br />

with the independent covariance structure since the comparison <strong>of</strong> maximized<br />

132

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