Statistical analysis of massive data is becoming indispensable to science, commerce, and society today. Such analysis requires efficient, flexible storage support and special optimization techniques. In this demo, we present RIOT (R with I/O Transparency), a system that extends R, a popular computing environment for statistical data analysis. RIOT makes R programs I/O-efficient in a way transparent to users. It features a flexible array storage manager and an optimization engine suitable for statistical and numerical operations. RIOT also seamlessly integrates with external database systems, offering additional opportunities for processing data that reside in databases by blurring the boundary between database and host-language processing. This demo will show how statistical computation can be effectively and efficiently handled by RIOT.