GRASS GIS manual: v.vect.stats

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NAME

v.vect.stats - Count points in areas, calculate statistics.

KEYWORDS

vector, database, attribute table

SYNOPSIS

v.vect.stats
v.vect.stats help
v.vect.stats [-p] points=name areas=name [type=string[,string,...]] [player=integer] [alayer=integer] [method=string] [pcolumn=name] [ccolumn=string] [scolumn=string] [fs=character|space|tab] [--verbose] [--quiet]

Flags:

-p: Print output to stdout, do not update attribute table; First column is always area category
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

points=name: Name of existing vector map with points
areas=name: Name of existing vector map with areas
type=string[,string,...]: Feature type; Feature type; Options: point,centroid; Default: point
player=integer: Layer number for points map; A single vector map can be connected to multiple database tables. This number determines which table to use.; Default: 1
alayer=integer: Layer number for area map; A single vector map can be connected to multiple database tables. This number determines which table to use.; Default: 1
method=string: Method for aggregate statistics; Options: sum,average,median,mode,minimum,min_cat,maximum,max_cat,range,stddev,variance,diversity
pcolumn=name: Column name of points map to use for statistics; Column of points map must be numeric
ccolumn=string: Column name to upload points count; Column to hold points count, must be of type integer, will be created if not existing
scolumn=string: Column name to upload statistics; Column to hold statistics, must be of type double, will be created if not existing
fs=character|space|tab: Field separator; Output field separator; Default: |

DESCRIPTION

v.vect.stats counts the number of points in vector map points falling into each area in vector map areas. Optionally statistics on point attributes in points are calculated for each area. The results are either uploaded to the attribute table of the vector map areas or printed to stdout.

OPTIONS

Statistical Methods: Using numeric attribute values of all points falling into a given area, a new value is detmined with the selected method. v.vect.stats can perform the following operations:

sum: The sum of values.
average: The average value of all point attributes (sum / count).
median: The value found half-way through a list of the attribute values, when these are ranged in numerical order.
mode: The most frequently occurring value.
minimum: The minimum observed value.
min_cat: The point category corresponding to the minimum observed value.
maximum: The maximum observed value.
max_cat: The point category corresponding to the maximum observed value.
range: The range of the observed values.
stddev: The statistical standard deviation of the attribute values.
variance: The statistical variance of the attribute values.
diversity: The number of different attribute values.

NOTES

Points not falling into any area are ignored. Areas without category (no centroid attached or centroid without category) are ignored. If no points are falling into a given area, the point count is set to 0 (zero) and the statistics result to "null".

The columns count_column and stats_column are created if not existing. If they do already exist, the count_column must be of type integer and the stats_column of type double.

AUTHOR

Markus Metz

Last changed: $Date: 2008-08-13 21:52:37 +0200 (Wed, 13 Aug 2008) $

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