In this model, the term \(\theta\) parameterises the strength and the
direction of the interaction between koalas. A value of \(\theta\ <1\)means repulsion, \(\theta=1\) means no interaction and \(\theta>1\)means aggregation. The term \(\varphi\) provides a measure of the
spatial scale of interaction. If \(\theta>1\) and \(\varphi\) is large
then koalas aggregate in large areas. When \(\theta>1\) and\(\varphi\) is small koalas aggregate in smaller areas.
The likelihood function given by the above equation was maximized using
a numerical optimization procedure implemented in the ”nlimnb” function
in the R (version 3.5.1) software environment. Since the model specified
was not available in any of the existing R packages, the algorithm used
in this analysis was developed in R.