Periodicity is defined as the character of being periodic; the tendency to recur at regular intervals. Applied to market data analysis and Investor/RT in particular, the periodicity of a chart relates to the manner by which the periodic intervals of market data are determined. All the trading within an interval is defined as a bar, each bar having an open price, high, low, close and volume of trading during the interval. This tutorial presents the extensive range of periodicities available in Investor/RT. Periodicities are grouped into three categories: time dependent, volume dependent, and price dependent.