The combination of index and matching function is to query the relationship between tables, find the position number of matching unit through matching function, and then use this position number to find the related value corresponding to matching value through index function. A similar method is to use the lookup function, but this function requires the data tables to be arranged in order.

Origin of function

The word "function" used in China's math book is translated. It was Li, an algebra expert in Qing Dynasty, who translated "function" into "function" when he translated Algebra (1859).

In ancient China, the word "Xin" and the word "Han" were universal and both had the meaning of "Han". Li's definition is: "every formula contains heaven, which is a function of heaven." In ancient China, four words were used to represent four different unknowns or variables: heaven, earth, people and things. The meaning of this definition is: "Whenever a formula contains the variable X, the formula is called a function of X."