NCERT Book Class 8 Maths Chapter 13 Introduction to Graphs

INTRODUCTION TO GRAPHS 157

CHAPTER

Introduction to Graphs
13
13.1 Introduction
Have you seen graphs in the newspapers, television, magazines, books etc.? The purpose
of the graph is to show numerical facts in visual form so that they can be understood
quickly, easily and clearly. Thus graphs are visual representations of data collected.
Data can also be presented in the form of a table; however a graphical presentation is
easier to understand. This is true in particular when there is a trend or comparison to
be shown.
We have already seen some types of graphs. Let us quickly recall them here.

13.1.1 A line graph
A line graph displays data that changes continuously over periods of time.
When Renu fell sick, her doctor maintained a record of her body temperature, taken
every four hours. It was in the form of a graph (shown in Fig 13.1 and Fig 13.2).
We may call this a “time-temperature graph”.
It is a pictorial representation of the following data, given in tabular form.

Time 6 a.m. 10 a.m. 2 p.m. 6 p.m.

Temperature(°C) 37 40 38 35

The horizontal line (usually called the x-axis) shows the timings at which the
temperatures were recorded. What are labelled on the vertical line (usually called
the y-axis)?