Secondary Axis for Scatter Plot?

Create the scatter plot with your x-values and first set of y-values. Select the second group of y-values in your table, and drag the selection to the chart. Drag the same selection to the chart a second time, and some new data points will appear (don't worry if they're not in the right location at this point).

Click on one of the data points from the second group. Now go to the Chart Inspector, choose the "Series" tab and edit the X-Data entry to reflect the same x-values range as for your first series of data.

After a little experimentation, there is a more elegant way to accomplish this.

Make a scatter chart from your x- and first y-column data. You'll see a small gear appear at the upper-left corner of your table data. Click on the gear and choose "Share X-values". Now grab the little bulls-eye at the lower-right corner of your selected data, and drag it to include the next series of data.

There is no option for a secondary axis on a scatter chart (at least not yet). The only advice I can offer is:

1. Scale one set of data so the two sets are in the same range. So, for example, instead of plotting "Data Set Two", plot "Data Set Two x 100"

2. Use a log scale on the Y axis.

There's no automatic way to put a secondary axis on a Scatter Chart, but that shouldn't stop you.

Add a Plain Table to your Sheet and adjust its size to one column, and with a number of rows equal to the number of horizontal grid lines you are using. Set the borders and fill of this new Table to None, type in your labels and position the Table to the right side of your Chart. Adjust the Font and Row Height, tweak the position of the Table. Create a new column for the data that you want to chart on your Secondary Axis and scale that data based on the ratio of the Secondary Axis to the Primary Axis. Assuming that you are sharing X-values as Brie suggested, you can then drag your scaled data to the Chart.

Jerry

That's a neat way to get around this problem. I would recommend for the left-side Y axis that you enter the min and max in the Table Inspector and not leave them as "auto". You don't want them adjusting by themselves later in the future.

This got me thinking. You can color-coordinate the text on the two Y axes so they are the same color as their respective lines. That makes it instantly recognizable on screen and on a color printout which axis goes with which data. With color coordination and a multi-column right side Y-axis table, you could add additional sets of Y axis labels for additional data series.