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

       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.

SEE ALSO

       v.random

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.

KNOWN ISSUES

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

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: 2015-05-11 02:16:13 +0200 (Mon, 11 May 2015) $

       Main index | Vector index | Topics index | Keywords index | Full index

       © 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual