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STCLASS—Spatiotemporal Distance Class Analysis Software for the Personal Computer. Scot C. Nelson, Assistant Professor, University of Hawaii at Manoa, Department of Plant Pathology, Honolulu 96822. Plant Dis. 79:643-648. Accepted for publication 20 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0643.

A software program (STCLASS) for DOS-based personal computers was developed to perform spatiotemporal distance class analysis of intensively mapped binary data. The program can be used to detect and quantify aspects of nonrandom patterns of disease increase in regularly spaced plant populations. Mapped disease incidence evaluations from two disease assessment dates (t1 and t2) are obtained for comparison with simulated (expected) data. Expected (random) maps for t2 are generated by retaining diseased plants from t1 in the exact spatial locations in which they were observed and by assigning the number of newly diseased plants observed at t2 to random spatial positions among the nondiseased plant population observed at t1. Distance class analysis is used to compare the expected paltern(s) to the observed pattern at t2. Program output includes a map of observed data and [X,Y] distance class matrices in nu-merical and graphical format. The distance class matrix consists of observed and expected standardized count frequencies for each [X,Y] distance class, the level of significance, and 95% upper and lower confidence intervals on significance levels. The program also can perform two-dimensional distance class analysis and can superimpose distance class matrices from two-dimensional and spatiotemporal distance class analyses of the same data set. The program alerts the user to nonrandom patterns of disease increase and edge effects. The software and a detailed user's manual are available free from the author.