hdd-package.Rdhdd offers a class of data, hard drive data, allowing the easy importation/manipulation of out of memory data sets. The data sets are located on disk but look like in-memory, the syntax for manipulation is similar to data.table. Operations are performed "chunk-wise" behind the scene.
The functions for importations is txt2hdd. The loading of a hdd data set is done with hdd and the data is extracted with sub-.hdd which has a data.table syntax. You can alternatively create a hdd data set with hdd_slice. Other utilities include hdd_merge, or peek to have a quick look into a text file containing data.