xenial (1) v.univar.1grass.gz

NAME

       v.univar  - Calculates univariate statistics of vector map features.
       Variance and standard deviation is calculated only for points if specified.

KEYWORDS

       vector, statistics, univariate statistics, attribute table, geometry

SYNOPSIS

       v.univar
       v.univar --help
       v.univar     [-gewd]     map=name      [layer=string]       [type=string[,string,...]]      [column=name]
       [where=sql_query]   [percentile=integer]   [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -g
           Print the stats in shell script style

       -e
           Calculate extended statistics

       -w
           Weigh by line length or area size

       -d
           Calculate geometric distances instead of attribute statistics

       --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

       type=string[,string,...]
           Input feature type
           Options: point, line, boundary, centroid, area
           Default: point,line,area

       column=name
           Name of attribute column

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

       percentile=integer
           Percentile to calculate (requires extended statistics flag)
           Options: 0-100
           Default: 90

DESCRIPTION

       v.univar  calculates  univariate statistics of vector map features.  This includes the number of features
       counted, minimum, maximum values, and range.  Variance and standard  deviation  is  calculated  only  for
       points if type=point is defined.

       Extended statistics (-e) adds median, 1st and 3rd quartiles, and 90th percentile to the output.

NOTES

       When  using  the  -d  flag,  univariate  statistics  of  vector geometry are calculated. Depending on the
       selected vector type, distances are calculated as follows:

           •   type=point: point distances are considered;

           •   type=line: the first point of each line is considered;

           •   type=area: the centroid of each area is considered.

EXAMPLE

       The example is based on the North Carolina sample dataset:
       g.region raster=elevation -p
       v.random output=samples npoints=100
       v.db.addtable map=samples columns="heights double precision"
       v.what.rast map=samples rast=elevation column=heights
       v.db.select map=samples
       Calculate height attribute statistics:
       v.univar -e samples column=heights type=point
       number of features with non NULL attribute: 100
       number of missing attributes: 0
       number of NULL attributes: 0
       minimum: 57.2799
       maximum: 148.903
       range: 91.6235
       sum: 10825.6
       mean: 108.256
       mean of absolute values: 108.256
       population standard deviation: 20.2572
       population variance: 410.356
       population coefficient of variation: 0.187123
       sample standard deviation: 20.3593
       sample variance: 414.501
       kurtosis: -0.856767
       skewness: 0.162093
       1st quartile: 90.531
       median (even number of cells): 106.518
       3rd quartile: 126.274
       90th percentile: 135.023
       Compare to statistics of original raster map:
       r.univar -e elevation
       total null and non-null cells: 2025000
       total null cells: 0
       Of the non-null cells:
       ----------------------
       n: 2025000
       minimum: 55.5788
       maximum: 156.33
       range: 100.751
       mean: 110.375
       mean of absolute values: 110.375
       standard deviation: 20.3153
       variance: 412.712
       variation coefficient: 18.4057 %
       sum: 223510266.558102
       1st quartile: 94.79
       median (even number of cells): 108.88
       3rd quartile: 126.792
       90th percentile: 138.66
       Calculate distance between sampling points statistics:
       v.univar -d samples column=heights type=point
       number of primitives: 100
       number of non zero distances: 4851
       number of zero distances: 0
       minimum: 69.9038
       maximum: 18727.7
       range: 18657.8
       sum: 3.51907e+07
       mean: 7254.33
       mean of absolute values: 7254.33
       population standard deviation: 3468.53
       population variance: 1.20307e+07
       population coefficient of variation: 0.478132
       sample standard deviation: 3468.89
       sample variance: 1.20332e+07
       kurtosis: -0.605406
       skewness: 0.238688

SEE ALSO

        db.univar, r.univar, v.db.univar, v.neighbors

AUTHORS

       Radim Blazek, ITC-irst

       extended by:
       Hamish Bowman, University of Otago, New Zealand
       Martin Landa

       Last changed: $Date: 2015-01-01 13:07:46 +0100 (Thu, 01 Jan 2015) $

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