
269Spatial Point Patterns
(a continuous mark). Of great interest, in addition to the spatial distribution, is how the values or
marks relate to each other over the domain given the spatial structure of the point pattern.
As illustrated in Figure 8.10, there are several ways of depicting the marks. For example, we can
make the symbol size proportional to the value of a continuous variable (top panels). This sufces
when all values are positive (top left), but in addition we change symbol type for negative values
(top right). Alternatively, we can divide the range of the continuous variable into intervals (say
quartiles) and use different symbol ...