# chorley

##### Chorley-Ribble Cancer Data

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)

##### 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, 2005, from a photograph of an Ordnance Survey map.

##### 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`

.

##### References

Baddeley, A., Turner, R., *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
summary(chorley)
chorley.extra$plotit()
```

*Documentation reproduced from package spatstat, version 1.37-0, License: GPL (>= 2)*