[GRASSLIST:611] Re: How do I create a thematic map from a
jhamner at emory.edu
Thu Apr 6 17:13:37 EDT 2006
On Apr 6, 2006, at 4:15 PM, Jesse Hamner wrote:
> If the basin dbf has no attributes, you'll have to add your basin
> ID to the vector coverage first, and then you can merge the
> rainfall values with db.execute (or do it outside of GRASS using,
> say, MySQL).
> First add a column in the database for your unique ID. I'd use
> db.execute here too, or else do it outside of GRASS in a terminal
> To add basin IDs, use the d.what.vect -ef command, clicking through
> each basin and assigning the appropriate value to the "BASIN_ID"
> Last, as noted above, you can then (in MySQL, at least) Left- or
> Right-JOIN the tables WHERE index.table1 = index.table2. This type
> of JOIN has the added bonus of filling in missing values with NULL,
> so you can spot values you might have skipped.
> Alternately, you could create a "RAINFALL" field in your coverage
> dbf file (here, I'll call it 'tablename') and use
> UPDATE tablename SET 'tablename.RAINFALL'= 'othertable.rainfall'
> WHERE 'tablename.BASIN_ID' = 'othertable.basin_id';
> to merge in the one value; I think that's the right syntax--
> somebody tell me if I screwed up.
I should note that these SQL commands won't work with the dbf driver--
you'll have to db.connect to a mysql database and db.copy your
polygon attribute table into the database. Allen Hollander's solution
will work with the dbf driver, so that's a consideration.
More information about the grass-user