Grapher 13 has added a reduced major axis (RMA) fit method to the list of predefined fit methods. To use add this fit to your plot:
- Click on the Line/Scatter Plot in the Object Manager to select it.
- Click Graph Tools | Add to graph | Fit Curve. By default, a linear fit will be applied.
- Click on the Linear Fit in the Object Manager to select it.
- In the Property Manager, click on the Plot tab.
- Change the Fit type field to RMA.
Grapher 12 and previous do not have an automatic way to create the reduced major axis regression equation directly. However, there is a script available that does calculate the RMA equation and add it to your existing graph as a function plot. That script and instructions for running it are available here: https://support.goldensoftware.com/hc/en-us/articles/227835267-How-can-I-create-an-RMA-reduced-major-axis-fit-curve-in-a-Grapher-script-.
Updated October 08, 2018