bionic (1) v.db.univar.1grass.gz

NAME

       v.db.univar  - Calculates univariate statistics on selected table column for a GRASS vector map.

KEYWORDS

       vector, statistics, attribute table

SYNOPSIS

       v.db.univar
       v.db.univar --help
       v.db.univar        [-eg]       map=name        [layer=string]        column=name        [where=sql_query]
       [percentile=float[,float,...]]   [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -e
           Extended statistics (quartiles and 90th percentile)

       -g
           Print stats in shell script style

       --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

       column=name [required]
           Name of attribute column on which to calculate statistics (must be numeric)

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

       percentile=float[,float,...]
           Percentile to calculate (requires extended statistics flag)
           Options: 0-100
           Default: 90

DESCRIPTION

       v.db.univar calculates basic univariate statistics for numeric attributes in a vector attribute table. It
       will calculate minimum, maximum, range, mean, standard deviation,  variance,  coefficient  of  variation,
       quartiles, median, and 90th percentile.

       v.db.univar  uses  db.univar  which  in  turn  uses  db.select  to  get  the attribute values on which it
       calculates the statistics.  This means that statistics  are  calculated  based  on  the  entries  in  the
       attribute  table, not based on the features in the map. One attribute value is read from each line in the
       attribute table, whether there are no, one or several features with the category value referenced by that
       line, or whether any features have more than one category value.  For feature-based, instead of attribute
       table-based, univariate statistics on attributes see v.univar.   NOTES  A  database  connection  must  be
       defined for the selected vector layer.

EXAMPLES

   Univariate statistics on attribute table column
       In  this  example, the 30 years precipitation data table is statistically analysed (North Carolina sample
       dataset) and univariate statistics performed:
       # show columns of attribute table connected to precipitation map
       v.info -c precip_30ynormals
       # univariate statistics on 30 years annual precipitation in NC
       v.db.univar precip_30ynormals column=annual
        Number of values: 136
        Minimum: 947.42
        Maximum: 2329.18
        Range: 1381.76
        Mean: 1289.31147058823
        [...]

   Univariate statistics on randomly sampled data points
       In this example, random points are sampled from the elevation map (North  Carolina  sample  dataset)  and
       univariate statistics performed:
       g.region raster=elevation -p
       v.random output=samples n=100
       v.db.addtable samples column="heights double precision"
       v.what.rast samples raster=elevation column=heights
       v.db.select samples
       v.db.univar samples column=heights

SEE ALSO

        db.univar, r.univar, v.univar, db.select, d.vect.thematic

AUTHOR

       Michael Barton, Arizona State University

       and authors of r.univar.sh (Markus Neteler et al.)

       Last changed: $Date: 2017-06-22 16:00:16 +0200 (Thu, 22 Jun 2017) $

SOURCE CODE

       Available at: v.db.univar source code (history)

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       © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual