(I have only CC'ed to AI-GEOSTATS, not being subscribed to the other
On Mon, 22 Oct 2001 Basil_LOH@... wrote:
> Hi everyone,
> In Singapore, we define a dengue cluster (referring to an outbreak when
> dengue fever is spreading contagiously from one person to the next) as at
> least 2 cases (points) within 200 m of each other and within 3 weeks of
> incidence of each other. With about 2,000 cases so far this year, I have
> about about 80 clusters according to this definition.
> However, I suspect that the occurence of some clusters (especially the ones
> with just 2 or 3 cases) may be by chance, instead of an actual disease
> transmission happening. How can I test this? Possibly, a Monte Carlo
> simulation of some kind will help. Is there any software out there that can
> help to do this? SATScan has got some promising functions, unfortunately it
> deals with areal or polygon data and not point data (I think).
One possibility are the stkhat family of functions in Splancs, including
stmctest - a Monte-Carlo test of space-time clustering, see: Diggle, P.,
Chetwynd, A., Haggkvist, R. and Morris, S. 1995 Second-order analysis of
space-time clustering. Statistical Methods in Medical Research, 4,
Software to run this in R (www.r-project.org) is contributed as a package
to be found on the same site (maintained by me), in S-PLUS at the original
site: http://www.maths.lancs.ac.uk/~rowlings/Splancs/. The article is not
very easy to get at, a further short description can be found in: Bailey,
T. C. and Gatrell, A. C. 1995, Interactive spatial data analysis. Longman,
Harlow, pp. 122-125.
A student from Thailand (Wutjanun Muttitanon <nungeog@...>) also
drew my attention to an article I think using stkhat: Exploratory
space-time analysis of reported dengue cases during an outbreak in
Florida,Puerto Rico,1991-1992 Author : Amy C.Morrison and et al. Journal :
American Tropical Hygine ,Vol 58(3) pp287-298.
If you follow up this route using the splancs package for R, I'd be very
grateful for feedback to help improve its documentation and functionality.
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
and: Department of Geography and Regional Development, University of
Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland.
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