spatial statistics (Was: S-plus and Grass)

James Darrell McCauley mccauley at
Mon Jul 17 14:38:04 EDT 1995

Gillian Bowser (gillian at writes on 17 July 1995:
>databases, I cannot for the life of me, figure out why they don't cover
>spatial statistics, autocorrelation, Moran's Index, kriging, ansiotrophy,

Because it's not a *spatial* statistics package...

FWIW, you can calculate Moran's I and the Geary Ratio (plus their
standard errors) using v.autocorr (on a triangulation of sites from
s.geom). It will also spit out a W (connectivity) matrix.

Quadrat count statistics can be calculated using s.qcount,
  Fisher el al. (1922) Relative Variance,
  David & Moore (1954) Index of Cluster Size,
  Douglas (1975) Index of Cluster Frequency,
  Lloyd (1967) "mean crowding",
  Lloyd (1967) Index of patchiness, and
  Morisita's (1959) I (variability b/n patches)
(see Cressie, chapter 9)

Semivariogram modeling is possible with, m.svfit, and g.gnuplot
(no nested structures, sorry).

Plus there's some other statistical software for sites available:
s.univar, s.probplt, and s.normal (which includes a dozen or so
different tests of (log)normality and other alternatives).

Most of these programs are available at:
See also the tutorials

I disagree with the philosoply of one- and two-way links to stat
packages.  These types of functions should be available *in* GIS
packages, not in some third party program (free or otherwise). It's
great that S-plus may become linked to GRASS (as it is with ARC/INFO),
but I see these types of solutions as quick fixes. Why can't we
include this functionality *in* GRASS?  Sure keeps the price
down... :)

So, with all of that said, what other types of programs would you like
to see? (I'm not committing myself but just getting ideas for my
rainy-day hobby list :) If you can include a pointer to a public
domain src for this, please do. It significantly speeds up development.

Make sure that the methods suggested make sense for spatial
data. Remember Tober's first law ("everything is related to everything
else, but near things are more related than distant things") and the
assumption of independence by most traditional (non-spatial) methods.

Also FWIW, here's an interesting article (which I don't fully 
agree with, but still worth mentioning):

@Article{ anselin93,
  author = 	 "Luc Anselin and Rustin F. Dodson and Sheri Hudak",
  title = 	 "Linking {GIS} and Spatial Data Anlysis in Practice",
  journal = 	 "Geographic Systems",
  year = 	 "1993",
  volume = 	 "1",
  number = 	 "1",
  pages = 	 "3-23"

If you need spatial statistics ASAP and can't wait for recreational
programmers, you might check into SPACESTAT. It apparently has links to
ARC/INFO, IDRISI, OSU-MAP, and generic raster files (does this mean

James Darrell McCauley, PhD 
Agricultural & Biological Engineering mccauley at
Purdue University                     tel: 317.494.1198 fax: 317.496.1115

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