GRASS GIS manual: v.qcount

Note: A new GRASS GIS stable version has been released: GRASS GIS 7.4, available here.
Updated manual page: here

NAME

v.qcount - Indices for quadrat counts of vector point lists.

KEYWORDS

vector, statistics, point pattern

SYNOPSIS

v.qcount

v.qcount --help

v.qcount [-g] input=name [layer=string] [output=name] nquadrats=integer radius=float [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-g: Print results in shell script style
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

input=name [required]: Name of input vector map; Or data source for direct OGR access
layer=string: Layer number or name ('-1' for all layers); A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name.; Default: -1
output=name: Name for output quadrat centers map (number of points is written as category)
nquadrats=integer [required]: Number of quadrats
radius=float [required]: Quadrat radius

DESCRIPTION
NOTES
SEE ALSO
REFERENCES
KNOWN ISSUES
AUTHORS

DESCRIPTION

v.qcount chooses nquadradius ants circular quadrats of radius radius such that they are completely within the bounds of the current region and no two quadrats overlap. The number of points falling within each quadrat are counted and indices are calculated to estimate the departure of point locations from complete spatial randomness.

NOTES

This program may not work properly with lat-long data. It uses hypot() in two files: count.c and findquads.c.

REFERENCES

Complete Spatial Randomness and Quadrat Methods - GRASS Tutorial on v.qcount (only available as older file s.qcount-tutorial.ps)

General references include:

Noel A. C. Cressie. Statistics for Spatial Data. Wiley Series in Probability and Mathematical Statistics. John Wiley & Sons, New York, NY, 1st edition, 1991.
Brian D. Ripley. Spatial Statistics. John Wiley \& Sons, New York, NY, 1981.

References to the indices include:

F. N. David and P. G. Moore. Notes on contagious distributions in plant populations. Annals of Botany, 18:47-53, 1954.
J. B. Douglas. Clustering and aggregation. Sankhya B, 37:398-417, 1975.
R. A. Fisher, H. G. Thornton, and W. A. Mackenzie. The accuracy of the plating method of estimating the density of bacterial populations. Annals of Applied Biology, 9:325-359, 1922.
M. Lloyd. Mean crowding. Journal of Animal Ecology, 36:1-30, 1967.
M. Morista. Measuring the dispersion and analysis of distribution patterns. Memoires of the Faculty of Science, Kyushu University, Series E. Biology, 2:215-235, 1959.