Humberside Data on Childhood Leukaemia and Lymphoma
Spatial locations of cases of childhood leukaemia and lymphoma, and randomly-selected controls, in North Humberside. A marked point pattern.
data(humberside)
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 | |
| or a control. |
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.
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.)
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 Baddeley Adrian.Baddeley@curtin.edu.au, 2005, from a reprint of Cuzick and Edwards (1990).
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.
if(require(spatstat.geom)) {
humberside
summary(humberside)
plot(humberside)
plot(Window(humberside.convex), add=TRUE, lty=2)
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