Methods of showing statistical data
In geography, diagrams are those
conceptual sketches through which geography information and data is transferred
to the paper. These are called statistical diagrams. These are.
Line graph Bar Graph Pie
graph
Let us study these
diagrams in detail.
1. Line
graph
In this diagram, statistical data is
displayed with help of a line on the graph, therefore it is called line graph.
In this graph two variables are shown, one as variable quantity and other as a
constant. To construct a line graph, two lines are drawn meeting each other at
90 degrees. Horizontal line is called X-Axis (Rain, years, Distances etc.) and
measureable variable is placed on Y-Axis (Rain, Temperature, air pressure,
production etc.) To measure the values at Y-Axis, an appropriate scale is
determined. With the help of scale, values are marked in the form of dots for
each constant variable. Then these dots are joined by a line to prepare a line
graph.
Merits
of line graph
With the help of line graph more than
one variables can be compared easily, i-e we can compare the annual
temperatures and rainfall values or Karachi and Lahore, which is not possible
on bar and pie graph. Due to this property of line graph, it is preferred over
bar graph.
Line graph is the
best way to show decrease or increase in annual, monthly and daily productions
of various items. Besides this, line graph is also used to show weather
conditions, population, animal distribution, exports and imports of a country.
All these statistics are related to time, so these are better illustrated on a
line graph.
One line graph, we
can easily understand the fluctuations as well as the production of items.
Demerits
of line graph
Although
we can show average quantities and productions on line graph, we can not show percentages
on it. Percentages are better shown on pie graphs.
Although we can show
fluctuations in productions, we can not show total production of any item on
the line graph, i-e total annual rainfall of a place or total population of
country.
2. Bar graph
Bar Graph is widely in geography. In
this graph, we show quantities in the form of bars of equal width on equal
intervals. The height of the bar varies with quantity. Bars can be drawn both
vertically and horizontally. This method is very useful for comparison of
different quantities, i-e population of big cities of Pakistan, length of
canals, marks of students in a subject, imports and exports of country, areas
and productions etc. We can also shade and colour the bars.
Merits
of Bar graph
·
We can show total quantity of
production on the bar graph.
·
We can also compare different
quantities of the same item.
·
It is easy to show quantities on bar
graph.
Demerits of Bar graph
·
To show more than one item or
quantity, we have to draw multiple bars or a compound bar
·
It is possible to show value of only
one item on the bar graph.
·
We cannot show percentages on bar
graph.
3. Pie Graph
Sometimes geographical data is displayed in
circles or sectors of circle, i-e population or areas of a country or cities,
imports or exports, trade and percentages on it. When we have to show
quantities of same type in percentages, the circle is supposed to be divided in
100 parts and sectors are created with the help of following formula.
We can calculate the specific angle (Sector
of the circle) of the given percentage by another formula.
These sectors can be shaded or colored.
Merits of pie graph
·
Pie graph covers less space as
compared to line and bar graph. It presents a better comparison between
different quantities. We can also show the total quantity on this graph.
·
It shows the areas of different
countries in a better way which is not possible on line and bar graph. Pie
graph is preferred to show production of power resources, i-e electricity gas.
Demerits of pie graph
·
Pie graph is not suitable to show
weather data, i.e., distribution of temperature, rain and wind pressure.
Calculations of percentages
and division of circle into sectors are comparatively difficult and consuming.
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