The raw data is classified in various ways depending on the purpose. Generally data can be classified as follows:

• Chronological classification: When the data is grouped according to time, it is called as chronological classification, in such a classification, data are classified either in ascending or in descending order with reference to time such as years, quarters, months weeks days, etc. 
• Spatial classification: If the data are classified with reference to geographical locations such as countries, states, cities, districts, etc., it is called spatial classification. 
• Qualitative classification: When the data are classified on the basis of certain attributes or qualities like literacy, religion, gender, marital status etc., then it is called qualitative classification. These attributes can be classified on the basis of either the presence or the absence of a qualitative characteristic. 
• Quantitative classification: If the classification of data is done on the basis of certain characteristics like height, weight. age, income, marks of students etc., it is called as quantitative classification.