What data do you collect for a line graph?

Answer 1

Any data you want where there are two variables (measurable data items) - the actual data depends upon what line graph you are going to draw.

For example:

If you are wanting to show how far you have travelled whilst driving, then the x-axis would show time and the y-axis distance driven; at various times (say every 15 seconds = ¼ minute) you would note how far has been driven which would give a pair (time, distance) to plot.

If you want to show how long it takes to drive a distance, then the x-axis would show the distance and the y-axis time taken; at various distances (say every 1/10 mile) you would note how long it has taken to get that far, giving a pair (distance, time) to plot.

Alternatively you may be interested in how share prices change over time; here the x-axis would be the time and the y-axis the share price, with a series of pairs (time, price) plotted.

A comparative line graph can be plotted where there are two different variables which are related to a third, eg the prices of two different shares over time; or how the price of a share has varied over two different years.