Grapher's fit curves use the least squares fit method. Grapher does not have an automatic way to create the reduced major axis regression equation directly. However, RMA and least squares fit curves are related. There is a script available that does calculate the RMA equation and add it to your existing graph as a function plot. That script is attached to this article.

The downside to this method is that there is not a reported R^{2} value for the fit. However, some literature says that the R^{2} value is the same for the RMA fit as it is for the least squares fit method. So, if you create a line/scatter plot and add the *Linear* fit, the statistics for the linear fit are the same as the statistics for the RMA fit. You can then run the script to add the RMA fit curve to the graph.

To add an RMA (reduced major axis) fit to your graph:

- Create a 2D scatter plot from the data by clicking the
**Graphs | Create | Basic | Scatter Plot**() command. - Click the
**Developer | User Scripts | Create RMA fit curve**command. The script runs and the RMA curve is added to the graph. - To get the R
^{2}statistic, click on the line/scatter plot in the**Object Manager**. - In the
**Property Manager**, click on the**Plot**tab. - Click the
*Add/Edit*button next to the*Fits*command. - In the
**Fits**dialog, select*Linear, Y=B*X+A.* - Click
*Add*. - Click
*OK*. - Click on the
*Fit 1: Linear*fit curve in the**Object Manager**. - In the
**Property Manager**, click on the*Di**splay*button next to the*Report*option. The statistics appear in a report window. - Highlight the
*Coefficient of determination, R-sq'd*value*(*R^{2}) value in the report. - Click
**Edit | Copy**in the report window. - In the main plot window, click
**Home | Clipboard | Paste**. The value is pasted to the center of the plot window. You can click on the value and move it to the desired location or edit the text.

*Updated September 22, 2016*

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