Graphs with two Y-axes

More than one Y axis

When you plot several kinds of data on one graph, it is often useful to plot some data using a Y-axis on the left side of the graph and other data using a Y-axis on the right side of the graph. Note that you never can have more than one X-axis.

To create a second Y axis:

Double-click on an axis to open the Frame and Origin tab of the Format Axes dialog. Or click on the Format Axis tool in the Prism toolbar.

Select the tab for "Right Y axis" and choose how you want the axis to be formatted.

•	All data sets are initially graphed using the left Y-axis. Depending on the scale of the axis, the data points may or may not all be visible.

Just assign data sets to the right Y-axis, as explained below. Prism will automatically create the axis.

To plot data using the right Y-axis

Double-click on a data point or click on the Format Graph button on the Prism toolbar. At the bottom of the Appearance tab, select “Right Y axis”. Repeat for each data set to be plotted on the right Y-axis.

To create a graph with three Y-axes:

Prism does not allow three Y-axes. You can, however, create that effect with a bit of a workaround. Create a graph with no data. Hide the X-axis (one of the choices for axis frame). Delete all the titles, You are left with just a Y-axis. You can make that whatever scale makes sense. Now make a layout and put your real graph next to this bogus graph with only a Y axis. With some fussing to get the sizes to match, and the data scaled right, you can give the illusion you want. You'll need to tell Prism to plot all the data sets on either the right or left axis, so may need to transform your values to make this work well.