Say you're a R user and have this 150GB text file containing a great data set, critical for your research. This too large for memory file can hardly be worked with in R and you don't want to invest time into a data base management system. Scratching your head, you're wondering what to do... That's when the package hdd kicks in!
hdd offers a simple way to deal with out of memory data sets in R. The main functions are txt2hdd for importation and the method [.hdd for manipulation of the data in a similar way to data.table.
The idea of hdd is very simple and similar to other DBMS: The data sets are located on disk and split into multiple files (chunks), each "workable" in memory. Within R, hdd data sets look like in-memory and all operations are performed "chunk-wise" behind the scene. No more excuse not to work with large data sets in R!
For a step-by-step example, please see the walk-through.