DATA:      Both et van Wirdum (1981), Farjon et Wiertz (1989)
DIRECTORY: \CANOCO\SAMPLES\PERMUTIO\GRID
PROBLEM:   Effect of pH and water-depth on plant species in a wetland
ILLUSTRATION OF:
+ How to obtain a permutation test that accounts for spatial autocorrelation
  when sampling points are on a grid
+ How to check whether the grid dimensions are 5*4 or 4*5
+ How to specify a permutation of plots (i.e. pairs of samples)
_______________________________________________________________________________
FILE TYPE    |  FILE NAME    |         DESCRIPTION
-------------+---------------+-------------------------------------------------
 SPECIES     | grid_spe.dta  | 100 plant species in 20 plots arranged in 
             |               |  a 5*4 grid, sampled in 1977 and 1988
ENVIRONMENT  | grid_env.dta  | plot, strip and year indicators, pH and water 
             |               |  depth
 PROJECTS    | grid88.con    | toroidal permutation test of the pH effect on
             |               |  the samples from 1988 only (5*4 grid)
             | grid_err.con  | as above but with wrong grid dimensions (4*5)
             | grid7788.con  | toroidal permutation test of paired samples to 
             |               |  test the pH effect on all samples (5*4 grid)
             | whol_err.con  | wrong attempt to test the pH effect, namely by
             |               |  permutation within sample pairs
-------------+---------------+-------------------------------------------------

Both, J.C. & Van Wirdum, G.(1981): Waterhuishouding, bodem en vegetatie van
enkele Gelderse natuurgebieden, RIN-report nr. 81/18. Rijksinstituut voor
Natuurbeheer, Leersum.

Farjon, A. & Wiertz, J.(1989): Milieu- en vegetatieverandering in het
schraalland van Koolmansdijk (gemeente Lichtenvoorde) 1952-1988. 
RIN-rapport 89/18. Rijksinstituut voor Natuurbeheer (Leersum).