The various types of diagrams are discussed below:

(1) Time-based line (curve) diagram:

• This diagram is used when we have some time related data. For example, price of a given share in last 30 days, number of vehicles passing through a cross road every hour of a day, growth of population from 1951 to 2001, etc.
• The line-diagram represents the relation between the two economic two variables and the slope.
• Line-diagram can be used for showing the demand curve, supply curve, etc.
• The independent variable (usually, time) is measured on ‘X-axis’ and the dependent variable is measured on ‘Y-axis’.

(2) Bar diagram:

A bar diagram is a chart that uses bars to show comparison between catcyories of data. The bars can be either horizontal or vertical.

Purpose:

• A bar diagram shows distribution of the value of a variable in various sections. For example, literacy rate in a country in various years or literacy rate among females and males in a particular year.
• A vertical or horizontal bar is drawn for each value of the variable.
  A separate bar is drawn for each section and the height/length of the bar indicates the value for that section.
• Thus, by comparing the height/length of the bars a comparison can be made of the values of each section.

Bar diagrams are generally of three types:

(A) Simple bar diagram
(B) Clustered bar diagram
(C) Divided bar diagram.

(A) Simple bar diagram:

• A simple bar diagram is a bar diagram which represents values of only one variable over a base.
• Through simple bar diagram, one can represent data of sale in various regions, months or years, etc.
• The difference in the length of bars gives a visual effect of the difference in the value of the variable under study.

(B) Clustered bar diagram:

In this type of a diagram, values of a common variable and over a common base are displayed for more than one section of related parameters. Hence we get a cluster of bars for the same variable over various values/sections at the base.

Use in economics:

• Suppose a mobile store owner has two branches. If he wish to compare sales of each branch for a given period of time then he can use clustered bar diagram.
• Other example could be variable ‘year’ as the base and comparing literacy of two sections namely males and females. This will be a two clustered bar diagram and each pair of bar will show literacy rate of male as well as female.
• To separate the bars properly, the clustered bars are given either different colours or designs. Each value point is then represented on the bar.

(C) Divided bar diagram:

• Divided bar diagram is a bar diagram wherein each bar is divided into several segments to represent a set of quantities according to the different proportions of the total amount.
• In this diagram, every single value of the variable has sub divisions. Hence we get divisions in all the bars which represent a common variable and common base values.
• Each division of the bar is colored differently to distinguish between the divisions. Values are put on each division so that it is easily understood.

(3) Pie-diagram:

• A pie diagram (or a circle chart) is a circular statistical diagram which is divided into slices to illustrate numerical proportion.
• Division of a circle in degrees represents a pie diagram.
• If an entire circle is considered as universal set of an entire data and the different sections of this data are represented by dividing the circle in degrees proportional to the data then a pie diagram is obtained.
• Note that we can draw pie diagram for the similar type of data for which a bar diagrams can be drawn.
• The complete circle represents 360°. Hence, the entire data represents 360° and sections/divisions of the data are represented by dividing the circle in degrees proportional to each data section.

Formula for obtaining proportional degree for a section of data:
Degree =  Component value /Total value  × 360