As data-centric methods, machine learning heavily relies on the quality, size, and type of the data. The importance of data quality and data size is obvious. It is worth mentioning that data types play a crucial role in machine learning applications, since it determines the choice of algorithms, training cost, and model performance. Various methods exist to classify the data. Here, we adopt one of these approaches, which categorizes data into four primary types: numerical data, categorical data, time series data, and text data.