Difference between graphs and diagrams

Following differences may be noted between
diagrams and graphs:
(i) A graph helps to study the mathematical relation between two variables such as price and demand, income and consumption, time and population etc. On the other hand, diagrams are used for sake of comparison but not for studying the relation between two variables.
(ii) Graphs are more precise and accurate than diagrams. Diagrams furnish Only approximate information on the problem under study.
(iii) Graphs are used to present time series data
and frequency distributions. Diagrams are useful in presenting geographical or spatial series. Presentation of data through graphs is easier than through diagrams.