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

. a typical bar chart or graphThe 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.

YearCocoa production (Tons)
1960 1961 1962 1963 1964 1965 1966 19677,000 1,500 3,000 6,000 8,500 5,000 4,000 3,500

Solution

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

YearCocoa production (Tons)
1960 1961 1962 1963 1964 1965 1966 19677.0 1.5 3.0 6.0 8.5 5.0 4.0 3.5
  • 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.

TownsMale (m)Female (m)Total (m)
Uromi8060140
Ubiaja6050110
Ekpoma7030100
Irrua301545

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

  1. IRRIGATION AND DRAINAGE
  2. IRRIGATION SYSTEMS
  3. ORGANIC MANURING
  4. FARM YARD MANURE
  5. HUMUS
  6. COMPOST
  7. CROP ROTATION
  1. IRRIGATION AND DRAINAGE
  2. IRRIGATION SYSTEMS
  3. INCUBATORS
  4. MILKING MACHINE
  5. SIMPLE FARM TOOLS
  6. AGRICULTURAL MECHANIZATION
  7. THE CONCEPT OF MECHANIZATION
  8. PROBLEMS OF MECHANIZATION
  9. SURVEYING AND PLANNING OF FARMSTEAD
  10. IMPORTANCE OF FARM SURVEY
  11. SURVEY EQUIPMENT
  12. PRINCIPLES OF FARM OUTLAY
  13. SUMMARY OF FARM SURVEYING
  14. CROP HUSBANDRY PRACTICES

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.

Towns1960(tons)1970(tons)1980(tons)
Ibadan304050
Abeokuta403060
Akure507040

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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