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NAME

       v.rast.stats   -  Calculates univariate statistics from a raster map based on a vector map
       and uploads statistics to new attribute columns.

KEYWORDS

       vector, statistics, raster, univariate statistics, zonal statistics, sampling, querying

SYNOPSIS

       v.rast.stats
       v.rast.stats --help
       v.rast.stats [-cd] map=name   [layer=string]    [where=sql_query]   raster=name[,name,...]
       column_prefix=string[,string,...]    [method=string[,string,...]]     [percentile=integer]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -c
           Continue if upload column(s) already exist

       -d
           Create densified lines (default: thin lines)
           All cells touched by the line will be set, not only those on the render path

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name [required]
           Name of vector map
           Or data source for direct OGR access

       layer=string
           Layer number or name
           Vector features can have category values in different layers. This  number  determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 1

       where=sql_query
           WHERE conditions of SQL statement without ’where’ keyword
           Example: income < 1000 and population >= 10000

       raster=name[,name,...] [required]
           Name of input raster map to calculate statistics from

       column_prefix=string[,string,...] [required]
           Column prefix for new attribute columns

       method=string[,string,...]
           The methods to use
           Options:  number,  null_cells,  minimum,  maximum,  range,  average, stddev, variance,
           coeff_var, sum, first_quartile, median, third_quartile, percentile
           Default:
           number,null_cells,minimum,maximum,range,average,stddev,variance,coeff_var,sum,first_quartile,median,third_quartile,percentile

       percentile=integer
           Percentile to calculate
           Options: 0-100
           Default: 90

DESCRIPTION

       v.rast.stats calculates basic univariate statistics from a raster map only for  the  parts
       covered  by  the specified vector map.  The vector map will be rasterized according to the
       raster map resolution.  Then univariate statistics  are  calculated  per  vector  category
       (cat)  from  the raster map and the results uploaded to the vector map attribute table.  A
       new column is generated in the attribute table for each statistic requested in method  (if
       not already present).

       The univariate statistics include the number of raster cells counted, the number of raster
       NULL cells counted, minimum and maximum cell values, range, average,  standard  deviation,
       variance,  coefficient  of  variation,  sum,  first  quartile, median, third quartile, and
       percentile.

NOTES

       v.rast.stats is only meaningful for lines or polygons.

       The module may take a long time to run if the raster region contains  a  large  number  of
       cells. In this case the --verbose flag may be used to track progress.

       The  script  stops  if  a  (prefixed)  upload  column is already present in the vector map
       attribute table, unless otherwise instructed with the -c continue flag. The column  prefix
       will be separated from the statistic name with an underscore. For example with a prefix of
       "elev" the sum column will be named elev_sum.

       If a DBF database is being used,  note  that  column  names  are  restricted  by  the  DBF
       specification to 10 characters. Therefore it is advised to be economical in the use of the
       column prefix when using DBF as any additional characters will be chopped off.

       If a MASK is present, it will be restored after the script finished.  The  script  changes
       temporarily to the resolution of the given raster map.

       Large    amounts    of    system   memory   can   be   used   when   extended   statistics
       (first_quartile,median,third_quartile,percentile ) are being requested with a  very  large
       region  setting.  If  the  region is too large the module should display memory allocation
       errors. Basic statistics can be calculated using any size input region.

EXAMPLES

       Example to upload DEM statistics to ZIP codes vector map (North Carolina sample dataset):
       g.copy vect=zipcodes_wake,myzipcodes_wake
       # set computational region to DEM:
       g.region raster=elevation -p
       # calculate selected DEM statistics, upload to vector map table:
       v.rast.stats myzipcodes_wake raster=elevation \
         column_prefix=elev method=minimum,maximum,average,range,stddev,percentile \
         percentile=95
       # verify results:
       v.info -c myzipcodes_wake
       v.db.select myzipcodes_wake
       v.univar myzipcodes_wake column=elev_range type=centroid

SEE ALSO

        r.univar, v.univar, v.vect.stats, v.what.rast, v.what.rast3, v.what.vect

AUTHOR

       Markus Neteler, CEA (for the EDEN EU/FP6 Project)

       Last changed: $Date: 2018-05-03 22:08:30 +0200 (Thu, 03 May 2018) $

SOURCE CODE

       Available at: v.rast.stats source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual