A new GRASS program to calculate autocorrelation statistics,

v.autocorr, is ready for testing. It is available via anonymous ftp from

pasture.ecn.purdue.edu:pub/mccauley/v.autocorr.shar.Z

It will probably be put on moon.cecer.army.mil in the very

near future.

I have tested it based upon examples in:

Daniel A. Griffith, (1987). Spatial Autocorrelation - A Primer.

Association of American Geographers.

and it seems to be working fairly well. It works only for GRASS

binary vector files labeled with numeric attributes.

****To those who know what spatial autocorrelation is:****

This program calculates a Geary Ratio and Moran Coefficient, standard

errors of each under both randomization and normalization, estimated

population means (Monte Carlo simulation) for both stats under both

assumptions, and Z statistics for testing Ho: spatial

autocorrelation exists. It also optionally outputs a connectivity

matrix.

Planned enhancements include:

o calculation of Wilk-Shapiro statistics at various places in the code

(e.g., during Monte Carlo simulation, to make sure that I am sampling

enough to get a good estimate of population means).

o calculation of population sizes (perhaps someone might need this for

something)

o calculation of some measure of sparseness (suggestions?) for the

connectivity matrix.

****To programmers:****

There's some nifty statistical functions from statlib which I have

ported to K&R C (approx 32 different flavors of random number

generators) included in this code. Deviates can be calculated from

Beta, Chi-square, Exponential, F, Gamma, Multivariate Normal, and many

other distributions. Documentation for these is included.

--

James Darrell McCauley Department of Ag Engr, Purdue Univ

mccauley@ecn.purdue.edu West Lafayette, Indiana 47907-1146

** "Do what is important first, then what is urgent." (unknown) **

P.S. due to time constraints, I regret that I cannot mail to those

without access to anonymous ftp. Try asking a friend if you

fit into this category.