What is Time Series Analysis?
Many types of models are created from individual samples of data. We may have conducted a study, collected vital signs from different patients, and are now fitting some predictive model. These patients are unique and independent cases, which collectively make up a trend. However, many kinds of systems are not collections of individual data points; they are a sequence of observations of one concept over time. The fluctuations in the stock market, global temperatures, oil sales, activity of solar flares, and so on are not baskets of different observations, but rather they are sequences of the same object through time. Thus, we would like to model how this object changes over time. When we consider time and past observations of a variable to model how it behaves and make forecasts, this is called a time series analysis.