data(chorley)chorley is
an object of class "ppp"
representing a marked point pattern.
Entries include
x Cartesian $x$-coordinate of home address
y Cartesian $y$-coordinate of home address
marks factor with levels larynx and lung
indicating whether this is a case of cancer of the larynx
or cancer of the lung.
}
See ppp.object for details of the format. The dataset chorley.extra is a list with two components.
The first component plotit is a function which will
plot the data in a sensible fashion. The second
component incin is a list with entries x and y
giving the location of the industrial incinerator.
Coordinates are given in kilometres, and the resolution is 100 metres (0.1 km)
The data were first presented and analysed by Diggle (1990). They have subsequently been analysed by Diggle and Rowlingson (1994) and Baddeley et al. (2005). The aim is to assess evidence for an increase in the incidence of cancer of the larynx in the vicinity of the now-disused industrial incinerator. The lung cancer cases serve as a surrogate for the spatially-varying density of the susceptible population.
The data are represented as a marked point pattern, with the points giving the spatial location of each individual's home address and the marks identifying whether each point is a case of laryngeal cancer or lung cancer.
Coordinates are in kilometres, and the resolution is 100 metres (0.1 km).
The dataset chorley has a polygonal window with 132 edges
which closely approximates the boundary of the Chorley and South
Ribble Health Authority.
Diggle, P. (1990) A point process modelling approach to raised incidence of a rare phenomenon in the vicinity of a prespecified point. Journal of the Royal Statistical Soc. Series A 153, 349-362.
Diggle, P. and Rowlingson, B. (1994) A conditional approach to point process modelling of elevated risk. Journal of the Royal Statistical Soc. Series A 157, 433-440.