Hi Barry, just a curiosity. Do you simply need a cloropleth with rainfall amount/rate coloring, or you have to do more complex operations?
2008/10/9 Barry Rowlingson <[EMAIL PROTECTED]>: > Hi All, > > I'm now very impressed with PostGIS and what it can do with spatial > data. Given the easy setup with Ubuntu, the easy admin with pgAdmin3, > and the great interface with Qgis, I'm won over totally. > > Of course I still need to read my spatial data into R (until I do all > my analysis in Python....). > > I'm trying to follow best practice with my database. So for any set > of polygons I have one table with the geometry and other tables with > data. I can create maps of the data by creating views where the data > table is linked to the geometry table via the polygon id. However some > of my views have many entries per polygon... > > For example I have monthly rainfall for 100 regions in Ethiopia over > 5 years - so that's a data table with 12*100*5 rows. If I read that as > an sp object (via readOGR) I will end up with a 6000-row sp-object, > containing 60 copies of each of the 100 polygon boundaries. That > doesn't sound good to me. > > What I want to do with this data is draw 60 choropleth maps - one for > each month. I can think of four approaches: > > 1. Suck it up - read the whole thing into an sp object and then > subset that by month for the map. Hope R doesn't fall over. > > 2. Read the map (without attached data) into an sp object and read > the data (without map geometry) into a data frame (using RPgSQL). Then > attach each month to the sp object. > > 3. As (2), but attach the whole dataframe to the sp-object and then > subset. Probably not much different from (2) really. > > 4. Can I apply an SQL select to the readOGR call, so I only select a > map with a single month's rainfall? I've just thought of this one. I'm > not sure if the specification of a PostGIS layer allows it. > > Any thoughts? > > Barry > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@stat.math.ethz.ch > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
