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NAME

       v.category  - Attaches, deletes or reports vector categories to map geometry.

KEYWORDS

       vector, category, layer

SYNOPSIS

       v.category
       v.category --help
       v.category   [-gt]  input=name   [layer=string[,string,...]]    [type=string[,string,...]]
       [ids=range]   [output=name]  option=string  [cat=integer]   [step=integer]   [--overwrite]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -g
           Shell script style, currently only for report
           Format: layer type count min max

       -t
           Do not copy attribute table(s)

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

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

       layer=string[,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, face, kernel
           Default: point,line,centroid,face

       ids=range
           Feature ids (by default all features are processed)
           Example: 1,3,7-9,13

       output=name
           Name for output vector map

       option=string [required]
           Action to be done
           Options: add, del, chlayer, sum, report, print, layers, transfer
           add: add a category to features without category in the given layer
           del: delete category (cat=-1 to delete all categories of given layer)
           chlayer: change layer number (e.g. layer=3,1 changes layer 3 to layer 1)
           sum: add the value specified by cat option to the current category value
           report: print report (statistics), in shell style: layer type count min max
           print: print category values, layers are separated by ’|’, more cats in the same layer
           are separated by ’/’
           layers: print only layer numbers
           transfer:  copy  values from one layer to another (e.g. layer=1,2,3 copies values from
           layer 1 to layer 2 and 3)

       cat=integer
           Category value
           Default: 1

       step=integer
           Category increment
           Default: 1

DESCRIPTION

       v.category attaches, copies, deletes or reports categories  of  vector  geometry  objects.
       Further on, v.category adds a number given by the cat option to categories of the selected
       layer.  These categories (IDs) are used to assign IDs or to group  geometry  objects  into
       categories  (several different geometry objects share the same category). These categories
       are also used to link geometry object(s) to attribute records  (from  an  attribute  table
       linked to vector map).

NOTES

       Use v.to.db to upload related categories to a linked attribute table.

       The  type parameter specifies the type of geometry objects to which the category is added;
       it is similar to an input filter - only the geometry specified in ’type’ is processed.

       If the type parameter is set to  centroid  and  the  option  parameter  set  to  add,  new
       categories will be added to existing centroids. Note however, that new centroids cannot be
       created this way.  To do so, they must be added manually using wxGUI vector  digitizer  or
       by running v.category with the type parameter set to area.

       If  categories  are copied with option=transfer, a warning is issued if categories already
       exit in the layer they are copied to. In this case the user must make sure beforehand that
       copying  categories  from  one layer to another layer does not cause undesired grouping of
       different geometry objects into the same categories. This can  be  avoided  by  specifying
       only  one  layer. The module will then find the next free layer number and copy categories
       to there. The new layer number is reported at the end.

       Areas are a special case because it is impossible to attach a cat to  an  area  without  a
       centroid;  in  this  case,  the  module  places  new  centroids in areas automatically for
       type=area.

       The cat parameter is only used with option=add, option=sum and option=del.

       Categories can be deleted for the given layer with option=del.  If cat is set to  -1,  all
       categories for the given layer are deleted. If cat is zero or positive, only this category
       value will be deleted. By default, cat is set to 1 which means  that  only  categories  of
       value 1 will be deleted.

       With  option=report,  the  module  reports  for  each  layer  and type the total number of
       categories, the minimum and the maximum category number. If there are e.g. two lines  with
       line  1  having category 1 and line 1 having categories 1 and 2, then there are a total of
       three category values with minimum 1 and maximum 2.

       The ids parameter specifies the list of feature IDs to which the operation  is  performed;
       by  default, all vector feature ids are processed.  The feature ID is an internal (unique)
       geometry ID that all vector primitives possess, and is  separate  from  any  category  the
       feature may also possess.  Use
         v.edit map=inputname tool=select
       to find out the geometry ids of certain features.

EXAMPLES

   Report vector categories
       v.category input=testmap option=report
       LAYER/TABLE 1/testmap:
       type       count        min        max
       point          0          0          0
       line        1379          1       1379
       boundary       0          0          0
       centroid       0          0          0
       area           0          0          0
       all         1379          1       1379

   Delete all vector categories in layer 1
       v.category input=testmap output=outmap option=del cat=-1

   Add vector categories in layer 1 with step=2
       v.category input=outmap output=stepmap option=add step=2
       # report
       v.category input=stepmap option=report
       LAYER/TABLE 1/outmap:
       type       count        min        max
       point          0          0          0
       line        1379          1       2757
       boundary       0          0          0
       centroid       0          0          0
       area           0          0          0
       all         1379          1       2757

   Add categories/centroids to a vector map without categories
       v.category input=wkt output=wktnew option=add
       Results can be tested using d.what.vect.

   Copy categories from layer 1 to layer 2,3,4,5,6,7 and 8
       Existing layer will be overwritten, non-existing will be created.
       v.category input=observer output=observer_new option=transfer layer=1,2,3,4,5,6,7,8

   Print vector categories of given layer
       Print vector categories from the first layer, only for feature ids 1-50.
       v.category input=roads option=print layer=1 id=1-50

SEE ALSO

        v.centroids, v.db.connect, v.edit, v.to.db

AUTHOR

       Radim Blazek, ITC-irst, Trento, Italy
       Modified  (the id parameter) by Martin Landa, FBK-irst (formerly ITC-irst), Trento, Italy,
       2008/02

       Last changed: $Date: 2018-09-15 22:00:54 +0200 (Sat, 15 Sep 2018) $

SOURCE CODE

       Available at: v.category source code (history)

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