Create line graphs

A line graph represents how a measured quantity changes across an ordered variable, often time, by placing ordered pairs on a coordinate grid and connecting successive points with line segments. Accurate construction requires choosing and labeling appropriate, evenly spaced scales, plotting values at their corresponding horizontal positions, and understanding that steepness and direction show the rate and direction of change between observations; it does not justify assuming exact values between points unless interpolation is warranted by the context.

Detailed Explanation: Create line graphs

A line graph shows how a measured quantity changes across an ordered set of values, such as days, months, or time.

Example

A student records the temperature at noon for five days.

Day	Temperature
Monday	$(10^\circ\text{C})$
Tuesday	$(12^\circ\text{C})$
Wednesday	$(15^\circ\text{C})$
Thursday	$(14^\circ\text{C})$
Friday	$(18^\circ\text{C})$

Step 1: Draw and label the axes

Draw a horizontal axis, called the $x$ -axis. Label it Day.
Draw a vertical axis, called the $y$ -axis. Label it Temperature $((^\circ\text{C}))$ .

Put the days in order from left to right:

\text{Monday, Tuesday, Wednesday, Thursday, Friday}

Step 2: Choose an even scale

The temperatures range from $(10^\circ\text{C})$ to $(18^\circ\text{C})$ . Use a scale that increases evenly, such as:

0,\ 5,\ 10,\ 15,\ 20

Each equal space on the vertical axis represents $(5^\circ\text{C})$ . An even scale makes the graph accurate.

Step 3: Plot the ordered pairs

Each day and temperature make an ordered pair:

(\text{Monday},10),\quad (\text{Tuesday},12),\quad (\text{Wednesday},15),\quad (\text{Thursday},14),\quad (\text{Friday},18)

Place a point above each day at the correct temperature.

For example, the Tuesday point goes above Tuesday and at $(12^\circ\text{C})$ .

Step 4: Connect successive points

Use a ruler to connect the points in order:

Monday to Tuesday
Tuesday to Wednesday
Wednesday to Thursday
Thursday to Friday

Do not connect the points in a different order.

Step 5: Read the graph

The graph shows that:

The temperature rose from Monday to Wednesday.
It fell slightly from Wednesday to Thursday.
It rose again from Thursday to Friday.
The steepest upward segment shows the fastest increase between two recorded days.

The line between two points shows the change from one observation to the next. It does not prove the exact temperature at every moment between those days unless the situation supports making an estimate.

Learn by doing: Create line graphs

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Graphing - Create Line Graph from Data (Text)

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