NAME

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

KEYWORDS

       vector, raster, statistics

SYNOPSIS

       v.rast.stats
       v.rast.stats help
       v.rast.stats  [-ce]  vector=name   [layer=integer]   raster=name  colprefix=string   [percentile=integer]
       [--verbose]  [--quiet]

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

       -e
           Calculate extended statistics

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       vector=name
           Name of vector polygon map

       layer=integer
           A  single vector map can be connected to multiple database tables. This number determines which table
           to use
           Default: 1

       raster=name
           Name of raster map to calculate statistics from

       colprefix=string
           Column prefix for new attribute columns

       percentile=integer
           Percentile to calculate (requires extended statistics flag)
           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.  New columns are generated in the attribute table if not
       already present.

       Nine columns are generated (n, min, max, range, mean, stddev, variance, coeff_var, sum) according to  the
       output  of r.univar.  If the -e extended statistics flag is given the 1st quartile, median, 3rd quartile,
       and given percentile are also calculated.

NOTES

       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 the -e extended statistics flag is used 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 rast=elevation -p
       # calculate DEM statistics, upload to vector map table:
       v.rast.stats myzipcodes_wake raster=elevation colprefix=elev
       # 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.what.rast, v.what.vect

AUTHOR

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

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

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                 v.rast.stats(1grass)