Multiple data series
Thus far we have only graphed one variable against another but there are many circumstances where we wish to graph more than one y-variable against the same x-variable. For our weather graph we might want to compare the cloud cover at two different cities. We now have data from two cities. The original city was Toronto, Canada. Now a friend has sent us the same type of data for Madrid, Spain.
To update our table we will insert a new row in the spreadsheet for a new heading, add some new column labels and the data from Madrid. Figure 65 presents our new data table.
Letâ€™s see how Toronto and Madrid compare. To do this we will add another data series to our existing graph. To makes things a bit easier to see, letâ€™s get rid of that regression line for the moment. SelectInsert > Statistics > No Regression.
To add the new column of data, right-click on the graph, select Modify Data Range and select the entire table again by dragging with the mouse and then click Create. We now have our two data series, but which one is which? We need a legend. Select Insert > Legend. The result is in Figure 66.