# Fit Curves

Fit curves are a collection of predefined mathematical functions that you can add to your graph to compare the behavior of your plot with known functions. In addition to the predefined fit curves, you can also create your own custom fit curves. Fit curves can be added to line/scatter plots, step plots, polar plots, and histograms; to 3D ribbon/wall, step plots, and histograms; and to 3D XYZ line/scatter plots and XYZ bar charts.

## Adding a Fit to a Plot

To add a fit to a plot:

- Select a plot in the Object Manager or plot window.
- Click the Graph Tools
| Add to Graph | Fit Curve command. A linear fit is added by
default when the command is clicked. Click the down arrow on the
**Graph Tools | Add to Graph | Fit Curve**command to select a specific fit type. The fit type can be changed in the Property Manager Plot page.

## Editing Fit Plot Properties

To change the features of a fit plot, including the number of points on the fit curve, open the fit plot properties by selecting the fit plot and editing the properties in the Property Manager. You may also add confidence intervals to a selected fit.

You can change the following fit plot properties:

Symbol (2D plots only)