After a satisfying meal of Chinese takeout, you absentmindedly crack open the complimentary fortune cookie. Glancing at the fortune inside, you read, "A dream you have will come true." Scoffing, you toss the small piece of paper and pop the cookie in your mouth. Being the intelligent, well-reasoned person you are, you know the fortune is insignificant--no one can predict the future. However, that thought may be incomplete.

AR models express the current value of the time series linearly in terms of its previous values and the current residual, whereas MA models express the current value of the time series linearly in terms of its current and previous residual series. ARMA models are a combination of AR and MA models, in which the current value of the time series is expressed linearly in terms of its previous values and in terms of current and previous residual series. The time series defined in AR, MA, and ARMA models are stationary processes, which means that the mean of the series of any of these models and the covariance among its observations do not change with time. For non-stationary time series, transformation of the series to a stationary series has to be performed first. ARIMA model generally fits the non-stationary time series based on the ARMA model, with a differencing process which effectively transforms the non-stationary data into a stationary one.

Time series analysis is the use of statistical methods to analyze time series data and extract meaningful statistics and characteristics of the data. In this blog, we will begin our journey of learning time series forecasting using python. We will be taking a small forecasting problem and try to solve it till the end learning time series forecasting alongside. Time series analysis is the collection of data at specific intervals over a period of time, with the purpose of identifying trends, cycles, and seasonal variances to aid in the forecasting of a future event. Data is any observed outcome that's measurable. Unlike in statistical sampling, in time series analysis, data must be measured over time at consistent intervals to identify patterns that form trends, cycles, and seasonal variances.