Two possible approaches come to mind...

**1. Create a stepped function using the Overlay Plot.**

Create a data table with columns for Power and Efficiency. To replicate my results, run the following script:

New Table( "Example",

Add Rows( 4 ),

New Column( "Power", Numeric, "Continuous",

Set Property( "Units", "W" ),

Set Values( [10, 12, 15, 17] )

),

New Column( "Efficiency", Numeric, "Continuous",

Set Property( "Units", "%" ),

Set Values( [90, 93, 97, 97] )

)

);

Then create an overlay plot (**Graph** > **Overlay**) where Y is Efficiency and X is Power. Finally, click on the red triangle and select **Y Options** > **Step**.

**2. Add a function to an existing graph.**

If you already have a graph (such as a Bivariate / Fit Y by X graph) containing data, right-click on the graph and select **Customize**.

In the Customize Graph window, click on the "**+**" button and paste the following script.

Y Function(

If(

10 < x <= 12, 90,

12 < x <= 15, 93,

15 < x <= 17, 97,

.

),

x

);

Then click OK.The function should be overlaid on the graph. Adjust axes if necessary.

Howard