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:
- Select the plot in the Object Manager.
- Click on the Plot page in the Property Manager.
- In the Add to Graph section, click Add/Edit next to Fit curve.
- Select Reduced Major Axis from the Available Fits list.
- Click Add to add this fit to the Display Following Fits list.
- Click OK to add the fit to the plot.
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 January 12, 2018