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v.vect.stats(1)		    GRASS GIS User's Manual	       v.vect.stats(1)

NAME
       v.vect.stats   -	Count points in	areas, calculate statistics from point
       attributes.

KEYWORDS
       vector, attribute table,	database, univariate statistics, zonal statis-
       tics

SYNOPSIS
       v.vect.stats
       v.vect.stats --help
       v.vect.stats  [-p]  points=name	areas=name  [type=string[,string,...]]
       [points_layer=string]   [points_cats=range]    [points_where=sql_query]
       [areas_layer=string]	[areas_cats=range]     [areas_where=sql_query]
       [method=string]	      [points_column=name]	   [count_column=name]
       [stats_column=name]     [separator=character]	[--help]   [--verbose]
       [--quiet]  [--ui]

   Flags:
       -p
	   Print output	to stdout, do not update attribute table
	   First column	is always area category

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       points=nameA [required]
	   Name	of existing vector map with points
	   Or data source for direct OGR access

       areas=nameA [required]
	   Name	of existing vector map with areas
	   Or data source for direct OGR access

       type=string[,string,...]
	   Feature type
	   Input feature type
	   Options: point, centroid
	   Default: point

       points_layer=string
	   Layer number	for points map
	   Vector features can have category values in different layers.  This
	   number determines which layer to use. When used with	direct OGR ac-
	   cess	this is	the layer name.
	   Default: 1

       points_cats=range
	   Category values for points map
	   Example: 1,3,7-9,13

       points_where=sql_query
	   WHERE conditions of	SQL  statement	without	 'where'  keyword  for
	   points map
	   Example: income < 1000 and population >= 10000

       areas_layer=string
	   Layer number	for area map
	   Vector  features can	have category values in	different layers. This
	   number determines which layer to use. When used with	direct OGR ac-
	   cess	this is	the layer name.
	   Default: 1

       areas_cats=range
	   Category values for area map
	   Example: 1,3,7-9,13

       areas_where=sql_query
	   WHERE  conditions of	SQL statement without 'where' keyword for area
	   map
	   Example: income < 1000 and population >= 10000

       method=string
	   Method for aggregate	statistics
	   Options: sum, average, median,  mode,  minimum,  min_cat,  maximum,
	   max_cat, range, stddev, variance, diversity

       points_column=name
	   Column name of points map to	use for	statistics
	   Column of points map	must be	numeric

       count_column=name
	   Column name to upload points	count
	   Column  to hold points count, must be of type integer, will be cre-
	   ated	if not existing

       stats_column=name
	   Column name to upload statistics
	   Column to hold statistics, must be of type double, will be  created
	   if not existing

       separator=character
	   Field separator
	   Special characters: pipe, comma, space, tab,	newline
	   Default: pipe

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 at-
       tributes	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.

       Statistical Methods: Using numeric attribute values of all points fall-
       ing 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 yet	exist-
       ing. If they do already exist, the count_column must be of type integer
       and the stats_column of type double precision.

       In  case	that v.vect.stats complains about the points_column of the in-
       put points vector map not being numeric,	the module v.db.update can  be
       used  to	perform	type casting, i.e. adding and populating an additional
       numeric column with the values type converted from string attributes to
       floating	point numbers.

EXAMPLES
   Preparation for examples
       The  subsequent	examples  are based on randomly	sampled	elevation data
       (North Carolina sample database):
       # work on map copy for attribute	editing
       g.copy vector=zipcodes_wake,myzipcodes_wake
       # set computational region: extent of ZIP code map, raster pixels
       # aligned to raster map
       g.region	vector=myzipcodes_wake align=elev_state_500m -p
       #  generate random elevation points
       r.random	elev_state_500m	vector=rand5000	n=5000
       v.colors	rand5000 color=elevation
       # visualization
       d.mon wx0
       d.vect myzipcodes_wake -c
       d.vect rand5000
       These vector maps are used for the examples below.

   Count points	per polygon with printed output
       See above for the creation of the input maps.

       Counting	points per polygon, print results to terminal:
       v.vect.stats points=rand5000 area=myzipcodes_wake -p

   Count points	per polygon with column	update
       See above for the creation of the input maps.

       Counting	of points per polygon,	with  update  of  "num_points"	column
       (will be	automatically created):
       v.vect.stats points=rand5000 area=myzipcodes_wake count_column=num_points
       # verify	result
       v.db.select myzipcodes_wake column=ZIPCODE_,ZIPNAME,num_points

   Average values of points in polygon with printed output
       See above for the creation of the input maps.

       Calculation of average point elevation per ZIP code polygon, printed to
       terminal	in comma separated style:
       # check name of point map column:
       v.info -c rand5000
       v.vect.stats points=rand5000 area=myzipcodes_wake \
	 method=average	points_column=value separator=comma -p

   Average values of points in polygon with column update
       See above for the creation of the input maps.

       Calculation of average point elevation per ZIP code polygon,  with  up-
       date  of	"avg_elev" column and counting of points per polygon, with up-
       date of "num_points" column (new	columns	 will  be  automatically  cre-
       ated):
       # check name of point map column:
       v.info -c rand5000
       v.vect.stats points=rand5000 area=myzipcodes_wake count_column=num_points \
	 method=average	points_column=value stats_column=avg_elev
       # verify	result
       v.db.select myzipcodes_wake column=ZIPCODE_,ZIPNAME,avg_elev

   Point statistics in a hexagonal grid
       The grid	extent and size	is influenced by the current computational re-
       gion. The extent	is based on the	vector map points_of_interest from the
       basic North Carolina sample dataset.
       g.region	vector=points_of_interest res=2000 -pa
       The hexagonal grid is created using the v.mkgrid	module as a vector map
       based on	the previously selected	extent and size	of the grid.
       v.mkgrid	map=hexagons -h
       The v.vect.stats	module counts the number of points and does  one  sta-
       tistics on a selected column (here: elev_m).
       v.vect.stats points=points_of_interest areas=hexagons method=average \
	 points_column=elev_m count_column=count stats_column=average
       User  should note that some of the points may be	outside	the grid since
       the hexagons cannot cover all the area around the edges	(the  computa-
       tional  region extent needs to be enlarged if all points	should be con-
       sidered).  The last command sets	the vector map color table to  viridis
       based on	the count column.
       v.colors	map=hexagons use=attr column=average color=viridis
       Point  statistics in a hexagonal	grid (count of points, average of val-
       ues associated with point, standard deviation)

SEE ALSO
	v.distance, r.distance,	v.rast.stats, v.what.vect, v.mkgrid

AUTHOR
       Markus Metz

SOURCE CODE
       Available at: v.vect.stats source code (history)

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

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.3 Reference	Manual

GRASS 7.8.3						       v.vect.stats(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHOR | SOURCE CODE

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