Vector Categories and Attributes

Viewing category values

To see information about the category values and labels of your vector file use:

• v.report : Generates statistics for vector files

• v.what : Query the category contents of a (binary) vector map layer at user-selected locations

Changing category values

As with raster maps you have to distinguish between changing an existing map's categories and creating a new map out of the categories of an old one. Contrary to raster maps, you can change the category numbers of existing vector maps:

• v.digit : A menu-driven, highly interactive map development program used for vector digitizing, editing, labeling and converting vector data to raster format (the universal tool for altering vector maps, also see the chapter called Digitizing Vector Maps for more information about v.digit)

• v.alabel : Bulk-labels unlabeled area features in a binary GRASS vector file (allows you to set category numbers and optionally labels)

• v.llabel : Bulk-labels unlabeled points or lines in a binary GRASS vector file (allows you to set category numbers and optionally labels)<

If you wish to create a new vector map on the basis of an old one, you can use one of two modules:

• v.reclass : Creates a new map layer whose category values are based upon the user's reclassification of categories in an existing vector map layer

• v.extract : Selects vector objects from an existing vector map and creates a new map containing only the selected objects