19.5 Brokenline graphs
Brokenline graphs are data graphs that represent data points joined by a line. It is important to note that
brokenline graphs are not the same as straightline graphs.
Example of a brokenline graph 
Example of a straightline graph 


Brokenline graphs are used to represent data that change continuously over time, such as the average daily
temperature for a week, or a person’s heartrate for a day (i.e. continuous data). Each data value is
represented by a point on the graph, and the points are joined by straight line segments to make a brokenline
graph.
Brokenline graphs are useful for identifying trends and patterns in data sets.
Worked Example 19.6: Drawing a brokenline
graph from a table
A group of friends went on a \(10\)hour hike. They recorded the temperature at certain times during the
hike. Represent the given information as a brokenline graph.
Time (hours) 
Temperature (\(^{\circ}\text{C}\)) 
\(0\) 
\(29\) 
\(2\) 
\(28\) 
\(5\) 
\(27\) 
\(7\) 
\(24\) 
\(10\) 
\(26\) 
Identify labels for the horizontal and vertical
axes.
The table shows the time and the corresponding temperature reading during the hike. The time (in hours)
will be on the horizontal axis and the temperature (in degrees Celsius) will be on the vertical axis. Notice
that the change in temperature depends on time.
Determine a suitable scale for the vertical axis.
First, we need to determine the range of temperature values. The lowest value is \(24 ^{\circ}\text{C}\)
and the highest value is \(29 ^{\circ}\text{C}\). So for the vertical axis we can use a scale from \(0
^{\circ}\text{C}\) to \(32 ^{\circ}\text{C}\) with intervals of \(2 ^{\circ}\text{C}\).
Draw the brokenline graph.
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Exercise 19.1
Use the brokenline graph to answer the following questions.
 What was the temperature after \(4\) hours?
 What was the minimum temperature during the \(24\)hour period?
 What was the temperature after \(10\) hours?
 What was the maximum temperature during the \(24\)hour period?
 At what time(s) was the temperature \(18 \text{ °C}\)?

\[16 \text{ °C}\]

\[10 \text{ °C}\]

\[22 \text{ °C}\]

\[26 \text{ °C}\]
 At \(7\) hours and \(18\) hours
Represent the data given below as a brokenline graph.
Time (\(\text{h}\)) 
Temperature (\(^{\circ}\text{C}\)) 
\(1\) 
\(25\) 
\(2\) 
\(28\) 
\(3\) 
\(30\) 
\(4\) 
\(31\) 
\(5\) 
\(34\) 
\(6\) 
\(36\) 
\(7\) 
\(37\) 
Use the table of values to draw a brokenline graph.
Time 
Heart rate (beats per minute) 
\(5\) a.m. 
\(68\) 
\(8\) a.m. 
\(91\) 
\(11\) a.m. 
\(83\) 
\(1\) p.m. 
\(92\) 
\(3\) p.m. 
\(87\) 
\(5\) p.m. 
\(95\) 