[R-sig-Geo] install rgdal to query postgis database

[Duncan McPherson]

I have installed postgres, postgis, gdal 'complete' all from kyngchaos. Then I loaded a map of England, and have been able to do manipulations of that with SQL statements. I can also create maps with QGis by loading Postgis layers within QGis. And, I can use the utilities in terminal, e.g.:

iMac:~ duncan$ ogrinfo -ro "PG:dbname=health_england user=postgres"
INFO: Open of `PG:dbname=health_england user=postgres'
      using driver `PostgreSQL' successful.
…[list of layers]

Further, I have installed R64 and RStudio, the packages DBI and RPostgreSQL and am able to query the non-map parts of the database:

> library(DBI)
> library(RPostgreSQL)
> con=dbConnect(dbDriver('PostgreSQL'), dbname="health_england", user="postgres")
> std<-data.frame(dbGetQuery(con, 'SELECT * FROM case_list LIMIT 10'), row.names=1)

Now the problem:

I need to be able to produce many maps from this database within R, so that I can, for example, use the non-map analyses above to colour the map areas. I want to do this programmatically because of the number of maps (also the reason for not wanting to save out a shapefile of every map), rather than produce each one in QGis. From reading around, including this: http://gis.stackexchange.com/questions/64950/which-is-the-best-way-of-working-with-postgis-data-in-r, that rgdal would be able to handle the database connection and correctly handle the geometry columns, which RPostgreSQL cannot. But I keep getting this:

> dsn="PG:dbname=england_health user=postgres"
> ogrListLayers(dsn)
Error in ogrListLayers(dsn) : Cannot open data source

Information that may be useful if you were to be able to help me might be:

> sessionInfo()
R version 3.0.1 (2013-05-16)
Platform: x86_64-apple-darwin10.8.0 (64-bit)

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] RPostgreSQL_0.4 DBI_0.2-7       rgdal_0.8-8     sp_1.0-9       

loaded via a namespace (and not attached):
[1] grid_3.0.1      lattice_0.20-15 tools_3.0.1    

> ogrDrivers()
             name write
...
42         PGDump  TRUE
43           PGeo FALSE
44     PostgreSQL  TRUE
...


> library(rgdal)
Loading required package: sp
rgdal: version: 0.8-8, (SVN revision 463)
Geospatial Data Abstraction Library extensions to R successfully loaded
Loaded GDAL runtime: GDAL 1.10.0, released 2013/04/24
Path to GDAL shared files: /Library/Frameworks/GDAL.framework/Versions/1.10/Resources/gdal
Loaded PROJ.4 runtime: Rel. 4.8.0, 6 March 2012, [PJ_VERSION: 480]
Path to PROJ.4 shared files: (autodetected)

Many thanks in anticipation,

Duncan