Introduction
Single-subject research has historically had an important position in the areas of research and practice evaluation. With the current trend toward evidence-based practice, the emphasis in this chapter is on the demand for and reliance on this practice-based, evidence-building research design to increase in the future. SSD for R is a software package available to help researchers and practitioners analyze single-subject research data. This chapter describes the historical, current, and future uses of single-subject research and the contributions of these designs to both visual and statistical analysis. A brief review of software packages to handle this type of analysis is included in this chapter. Finally, an overview of the functionality of SSD for R is provided.