Data classification

Data classification is the process of organising data into categories. In mathematics, data classification involves organising raw data into categories to make it easier to analyse. The main types are categorical (qualitative) data, which is descriptive and non-numerical, and numerical (quantitative) data, which is numerical. Numerical data is further broken down into discrete (countable, whole numbers) and continuous (measurable, can have any value). 

what does a graph need?