Dbase (DBF)

Some ML-Threads

Is there a simple way to join some attribute data in a comma separated text file to an existing GRASS vector map?

The data in the CSV file does not have any coordinates but a primary key field that also exists in the polygon map it needs to be joined to.

1. Answer 1:
   • use rdbms as data backend (including for the map you want the data to be connected to)
   • db.in.ogr
   • create view combining map attribute table with new table from csv-file (using key)
   • v.db.connect -o map table=NewView
2. Answer 2:
   • install SQLite (it does not need setup but works out of the box)
   • set the DBMI settings with db.connect (see manual page for copy-paste example)
   • use v.db.join
   • use g.copy or db.copy to easily transform from DBF (or whatever to SQLite).
3. Answer 3:
   • identify names and types of columns in csv file
   • v.db.addcol the relevant columns
   • for each line in csv file: v.db.update

Is there a tool which can convert a dBase file into a ASCII or CSV file?

1. Answer 1:
   • Freeware tool from a German website: [WinDBF32 Datenbank Editor http://www.buchenwald.de/software/index.html]
2. Answer 2:
   • ogr2ogr -f CSV output world.shp world
3. Answer 3:
   • db.out.ogr
4. Answer 4:
   • xbase
   • dbf
5. Answer 5:
   • dbftools
6. Answer 6:
   • OO.org Base instead of Calc (Calc may limit number of rows). See related Openoffice.org with SQL Databases
7. Answer 7:
   • dbview command line utility for converting to a flat ascii table

Is it safe to edit the DBF-table outside of GRASS in another program?

For instance in OpenOfficeCalc? Or even as a CSV with Python, IDL, etc.?

1. Answer:
   • Yes. You can actually create whatever dbf you want, wherever you want as long as it contains a column with the id's of the objects. Then you can connnect your vector map to this dbf with v.db.connect.

I need to do some calculations on my attribute tables. What is the corresponding command in GRASS for this?

1. Answer:
   • v.db.addcol
   • v.db.update