Add tested R query how-to and correct usage examples

README.md

@@ -46,6 +46,23 @@ SELECT term, decision_direction, COUNT(*) AS n
 FROM scdb.v_cases WHERE term >= 2015 GROUP BY 1, 2 ORDER BY 1, 2;
 ```
 
+### R with DBI and duckdb
+
+Install the dependencies once with `install.packages(c("DBI", "duckdb"))`.
+
+```r
+library(DBI)
+con <- dbConnect(duckdb::duckdb())
+dbExecute(con, "INSTALL httpfs")
+dbExecute(con, "LOAD httpfs")
+dbExecute(con, "ATTACH 'https://huggingface.co/datasets/Nason/scdb-database/resolve/main/scdb.duckdb' AS scdb (READ_ONLY)")
+dbGetQuery(con, "SELECT term, decision_direction FROM scdb.v_cases LIMIT 5")
+dbDisconnect(con, shutdown = TRUE)
+```
+
+DuckDB uses HTTP range requests; queries run on your machine and may need substantial memory or download data. A `LIMIT` does not guarantee a small scan.
+
+
 Or with the datapond packages: `pip install datapond` / `pak::pak("datapond-db/datapond-r")`.
 
 Build pipeline and caveats: https://github.com/ian-nason/scdb-database