doi:10.1016/j.csda.2006.11.039
Copyright © 2007 Elsevier B.V. All rights reserved.
Line and point cluster models for spatial health data
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Andrew B. Lawsona,
,
, Silvia Simeonb, Martin Kulldorffc, Annibale Biggerib and Corrado Magnanid
aDepartment of Epidemiology and Biostatistics, University of South Carolina, Columbia, USA
bDepartment of Statistics, University of Florence, Viale Morgagni, 59 Florence, Italy
cDepartment of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, 133 Brookline Avenue, 6th Floor, Boston, MA 02215, USA
dCentre for Cancer Epidemiology and Prevention Piedmont, Turin, Italy
Received 22 November 2005;
revised 30 November 2006;
accepted 30 November 2006.
Available online 6 February 2007.
Abstract
Spatial cluster modelling of small area disease incidence and mortality has previously focused on clusters where excess risk is distributed around fixed points, and the aim is the reconstruction of these points (cluster centers). Often there is a need to assess clusters of a different form, such as around roads or river systems. These clusters are often linear or can be approximated by combinations of several linear segments. In this paper the recovery of point and line clusters is considered jointly. An example application is given where both linear or point clustering could be present.
Keywords: Spatial; Clustering; Parametric; Modelling; Linear; Point
Fig. 1. The study window with the factory location given as (0,0). The case locations are denoted by
.
Fig. 2. The study region on the unit square with control locations (denoted by
) superimposed.
Fig. 3. Converged sample plots: (A) cusum convergence diagnostic (see text), (B) the βl posterior marginal density estimate, (C) histograms of the numbers of L-centers and (D) numbers of P-centers.
Fig. 4. Converged sample plots: (A) β the P-center rate parameter, (B) the control smoothing constant (h), (C) rl and (D) rp, the cluster variance parameters.
Fig. 5. Contour plot of the posterior marginal distribution of (A) the P-center locations, (B) the L-center locations, (C) contour plot of posterior exceedence probability (1-Pi) for a local likelihood cluster model applied to the Casale data.
Fig. 6. Simulation 1: panels row-wise from top left. (A) point and line case simulation, control simulation; L-center posterior marginal map for k=2; L-center posterior marginal map for k=8; L-center posterior marginal density for k=2; L-center posterior marginal density k=8. (B) A: L-center posterior marginal map for k=4; B: L-center posterior marginal density for k=4; C: L-center posterior marginal map for k=6; D: L-center posterior marginal density for k=6.
Fig. 7. Simulation 2: panels rowwise from top left: case events image&contour plot; control image&contour plot; L-center posterior marginal image&contour plot k=1; P-center posterior marginal image&contour plot n=2.

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