One of the most common tasks for an engineer or scientist is analysing data from an experiment. Sage provides a set of tools for loading, exploring, and plotting data. The following series of examples shows how a scientist might analyse data from a population of bacteria that are growing in a fermentation tank. Someone has measured the optical density (abbreviated OD) of the liquid in the tank over time as the bacteria are multiplying. We want to analyse the data to see how the size of the population of bacteria varies over time. Please note that the examples in this section must be run in order, since the later examples depend upon results from the earlier ones.