spatstat (version 1.48-0)

humberside: Humberside Data on Childhood Leukaemia and Lymphoma

Description

Spatial locations of cases of childhood leukaemia and lymphoma, and randomly-selected controls, in North Humberside. A marked point pattern.

Usage

data(humberside)

Format

The dataset humberside 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 case and control

indicating whether this is a disease case

See ppp.object for details of the format. The dataset humberside.convex is an object of the same format, representing the same point pattern data, but contained in a larger, 5-sided convex polygon.

Source

Dr Ray Cartwright and Dr Freda Alexander. Published and analysed in Cuzick and Edwards (1990), see Table 1. Pentagonal boundary from Diggle and Chetwynd (1991), Figure 1. Point coordinates and pentagonal boundary supplied by Andrew Lawson. Detailed region boundary was digitised by \adrian, 2005, from a reprint of Cuzick and Edwards (1990).

Notes

Cuzick and Edwards (1990) first presented and analysed these data. The data record 62 cases of childhood leukaemia and lymphoma diagnosed in the North Humberside region of England between 1974 and 1986, together with 141 controls selected at random from the birth register for the same period. The data are represented as a marked point pattern, with the points giving the spatial location of each individual's home address (actually, the centroid for the postal code) and the marks identifying cases and controls. Coordinates are expressed in units of 100 metres, and the resolution is 100 metres. At this resolution, there are some duplicated points. To determine which points are duplicates, use duplicated.ppp. To remove the duplication, use unique.ppp. Two versions of the dataset are supplied, both containing the same point coordinates, but using different windows. The dataset humberside has a polygonal window with 102 edges which closely approximates the Humberside region, while humberside.convex has a convex 5-sided polygonal window originally used by Diggle and Chetwynd (1991) and shown in Figure 1 of that paper. (This pentagon has been modified slightly from the original data, by shifting two vertices horizontally by 1 unit, so that the pentagon contains all the data points.)

References

J. Cuzick and R. Edwards (1990) Spatial clustering for inhomogeneous populations. Journal of the Royal Statistical Society, series B, 52 (1990) 73-104.

P.J. Diggle and A.G. Chetwynd (1991) Second-order analysis of spatial clustering for inhomogeneous populations. Biometrics 47 (1991) 1155-1163.

Examples

   humberside
   summary(humberside)
   plot(humberside)
   plot(Window(humberside.convex), add=TRUE, lty=2)