GRASS logo

Note: A new GRASS GIS stable version has been released: GRASS GIS 7. Go directly to the new manual page here

NAME

v.qcount - Indices for quadrat counts of sites lists.

KEYWORDS

vector, statistics

SYNOPSIS

v.qcount
v.qcount help
v.qcount [-gq] input=string [output=string] n=integer r=float [--overwrite] [--verbose] [--quiet]

Flags:

-g
Print results in shell script style
-q
Quiet
--overwrite
Allow output files to overwrite existing files
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

input=string
Vector of points defining sample points
output=string
Output quadrant centres, number of points is written as category
n=integer
Number of quadrats
r=float
Quadrat radius

DESCRIPTION

v.qcount chooses n circular quadrats of radius r 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.

SEE ALSO

v.random

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.

BUGS

Timestamp not working for header part of counts output. (2000-10-28)

Please send all bug fixes and comments to the author or the grass development team.
http://grass.osgeo.org.

AUTHORS

James Darrell McCauley <darrell@mccauley-usa.com>,
when he was at: Agricultural Engineering Purdue University

Modified for GRASS 5.0 by Eric G. Miller (2000-10-28)
Modified for GRASS 5.7 by R. Blazek (2004-10-14)

Last changed: $Date: 2011-11-08 01:42:51 -0800 (Tue, 08 Nov 2011) $

Main index - vector index - Full index

© 2003-2016 GRASS Development Team