11.3.4 Displaying Data on a Graph or Chart
You have seen that, provided you have both an x- and a y-coordinate, you can plot a point on a chart. So if a set of data consists of pairs of data values, then the data can be plotted on a graph.
For example, suppose a nurse is monitoring the weight of a woman during the last few weeks of her pregnancy and has recorded the woman’s weight each week as shown in the table below.
Weight of a Woman During Pregnancy
|Week of pregnancy||34||36||38||40|
|Weight in lb||166||170||172||173|
The second row heading, “Weight in lb,” tells us that the woman’s weight is expressed in lb (pounds).
So in week 34, the woman had a weight of 166 lb. This can be written as (34, 166) and plotted on a graph in the same way as the earlier examples.
If we take the x-coordinate of each point as the week of pregnancy and the y-coordinate as the weight in lb, then points can be plotted at (34, 166), (36, 170), (38, 172), and (40, 173) to represent this set of data.
Now we know how we are going to plot the points we need to decide how to draw the graph itself.