# BAR CHART OR GRAPHS AND THEIR USES

BAR CHART (OR GRAPHS) AND THEIR USES IN

What is a bar chart?

Bar chart or graph is a graph made up of bars of rectangles which are of equal width and whose lengths are proportional to the quantities they represent. The major characteristic of the bar chart is that the body of the bars must not touch each other. There must be a space or gap between one bar and another. Bar chart may be arranged vertically or horizontally.

## Types of bar charts or bar graph

There are three major types of bar charts. These are:

• Simple bar chart
• Component bar chart and
• Multiple bar chart

### Simple bar charts:

Simple bar chart (fig 2.4) is used when the data given are made up of only one item or component

. The bar chart can be presented by tabulated data with evenly spaced bars, separated by gaps with the length proportional to the magnitude of the value given.

### Exemplary use of a simple bar chart or bar graph

The table in 2.5 represents the quantity of cocoa production in Nigeria between 1960 and 1967. Represent the information or data by a bar chart.

Table 2.5(a): Cocoa production in Nigeria between 1960 and 1967.

Solution

Table 2.5(a): Cocoa production in Nigeria between 1960 and 1967.

• From the figures given, using the scale: 1cm: 1000 tonnes, the figures can be reduced to simple ones when they are divided by 1000.
• The new values will now be.

#### Useful information to be derived from using a bar graph

1. The year with the highest cocoa production can be calculated. The year is 1964
2. The year with the least cocoa production can also be calculated. The year is 1961.
3. The total cocoa production from 1960 to 1967 can be calculated, i.e. 7,000 + 1,500 + ……… + 4, 000 + 3, 000 = 38,500
4. The average or mean production can also be calculated by adding the total production (as in (iii) above) and dividing it by the number of years (8 years), i.e.

7,000 + 1, 5000 + ……. = 4,000 + 3,500 8 =38,500

8                = 4, 812.5 tons/year

## (b) what are Component bar charts

A component bar chart (fig. 2.5) is used when the data involved are of two variables.

Example

Represent the population of males and females (in millions) (table 2.6) in towns in Edo State in 1999 by a bar chart.

Solution

WEED AND THEIR BOTANICAL NAMES

1. ENVIRONMENTAL FACTORS AFFECTING AGRICULTURAL PRODUCTION
2. DISEASES
3. 52. SOIL MICRO-ORGANISMS
4. ORGANIC MANURING
5. FARM YARD MANURE
6. HUMUS
7. COMPOST
8. CROP ROTATION
9. GRAZING AND OVER GRAZING

Using a graph sheet, choose a suitable scale for the graph, e.g. 1cm represent 10 units, the graph (component bar chart in fig. 2.5) is then drawn.

COMPONENT BAR CHART SHOWING THE POPULATION OF SOME TOWNS

### MULTIPLE BAR CHART AND USAGE

b.         Multiple bar charts: The multiple bar chart (fig. 2.6) is used when there are about three or more variables in a given data. It has multiple bars, each of which stands for a component variable.

Example

Represent Nigeria’s export of cocoa (table 2.7) from Ibadan, Abeokuta and Akure in 1969, 1970 and 1980 by a bar chart.

Table 2.7: Nigeria’s export of cocoa from Ibadan, Abeokuta and Akure in 1960, 1970 and 1980.

Solution using bar chart

Using a graph sheet, choose a suitable scale for the graph, e.g. 1cm to represent 1o units, the graph (a multiple bar chart in fig. 2.6) is then drawn.

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