Prism lets you choose between fine, medium and course lowess curves. The fine curve reveals the fine structure of the data, but tends to wiggle a lot. The coarse curve shows only the general trend, but obscures the detail. Prism generates lowess curves using an algorithm adapted from Graphical Methods for Data Analysis , John Chambers et. Don't select a lowess curve unless you have well over twenty data points.
Prism generates the curve as a series of line segments.
Enter the number of segments you want, and check the option box if you need to see the XY coordinates of each point. Lowess curves can be too jagged. To get a smoother curve, consider using nonlinear regression and pick a model empirically. You don't have to pick a sensible model, and don't have to interpret the best-fit values. Use nonlinear regression to create a smooth curve, not as a method to analyze data.