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Re: AI-GEOSTATS: Spatial-temporal clustering by chance

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  • Roger Bivand
    (I have only CC ed to AI-GEOSTATS, not being subscribed to the other lists) ... One possibility are the stkhat family of functions in Splancs, including
    Message 1 of 2 , Oct 21, 2001
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      (I have only CC'ed to AI-GEOSTATS, not being subscribed to the other
      lists)

      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,
      124-136.

      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.

      Roger

      --
      Roger Bivand
      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
      e-mail: Roger.Bivand@...
      and: Department of Geography and Regional Development, University of
      Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland.




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