time series analysis

Historical data are often presented in the form of time series, such as China since the reform and opening up.The trend of CPI, the growth rate of GDP in the United States in the last 100 years, the highest and lowest temperatures recorded by meteorological station workers every day, the daily turnover of a commodity, the daily closing price of a stock, the company’s profits over the years, etc. These data all change with time, reflecting the development and changes of things and phenomena in time. They are data formed by the same thing or phenomenon at different times or periods, and they are called "time series data", or time series for short.