chorley {spatstat.data}

Chorley-Ribble Cancer Data

Description

Spatial locations of cases of cancer of the larynx and cancer of the lung, and the location of a disused industrial incinerator. A marked point pattern.

Usage

data(chorley)

Format

The dataset 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)

Notes

The data give the precise domicile addresses of new cases of cancer of the larynx (58 cases) and cancer of the lung (978 cases), recorded in the Chorley and South Ribble Health Authority of Lancashire (England) between 1974 and 1983. The supplementary data give the location of a disused industrial incinerator.

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.

Note that, due to the rounding of spatial coordinates, the data contain duplicated points (two points at the same location). To determine which points are duplicates, use duplicated.ppp. To remove the duplication, use unique.ppp.

Source

Coordinates of cases were provided by the Chorley and South Ribble Health Authority, and were kindly supplied by Professor Peter Diggle. Region boundary was digitised by Adrian Baddeley [e-mail], 2005, from a photograph of an Ordnance Survey map.

References

Baddeley, A., Turner, R., Moller, J. and Hazelton, M. (2005) Residual analysis for spatial point processes. Journal of the Royal Statistical Society, Series B 67, 617–666.

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.

Examples

    chorley
  if(require(spatstat.geom)) {
    summary(chorley)
    chorley.extra$plotit()
  }