[GRASSLIST:4006] Re: GRASS5.7

Du Chavoux Luyt educluyt at sun.ac.za
Fri Jul 23 10:27:30 EDT 2004


Dear GRASS list

I installed GRASS 5.7 and I'm really impressed! It looks like it can really do a lot more (at least on the vector and db side) than my old stable GRASS 5.03.

I'm working through the tutorial now and want some clarity on the whole importing of shape files; more specifiacally on the effect of subsequent v.extract command.
1. As I understand it, importing a shp file also copies the dbf table (to the local dbf directory) without changing it at all: is this correct?
2. When I do a v.extract using "where", I get a vector file with the subsection of the original as required. Do I also get a subsection of the "connected" dbf file somewhere? Is it possible to get such a subsection? (One alternative could be to write a generic SQL editor and repeat a corresponding SQL query on the dbf by itself).
3. According to the tutorial then I have to edit the db file:
#to use the new map, you should link attributes to it. This can
#be the table from the parent map. Edit the DB file and add a row for
#the new map (here: markveggy.1)
I have linked the parent dbf file and it works fine as far as I can tell. However. if I should want to do statistical analysis on the dbf file, I would need seperate files...(see question 2 above) I suppose this process isn't automated yet?
4. v.overlay would combine 2 vector files (union / intersection etc.) into a new vector file. Will it also create a connected dbf file for the new combined vector?

Thanks for all help so far.
Chavoux




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