How do I display all of the data points, but only fit a certain section of the curve?
Copy the data you want to fit and paste it into a new column. Then create a Line plot, using both Y columns of data. Hide the new variable by choosing No Markers and a Line Style of None in Variable Settings (Plot Menu). Apply the curve fit to this variable. The curve fit will be displayed, but the second set of points won’t be displayed.
An alternate method (as reported by one of our users) is to mask the unwanted cells in the original column. Create the plot and apply the curve fit to the remaining data. Go back to the data window and unmask the cells. Go back to the plot, choose Variable Settings, and click OK. The plot will be redrawn to include the unmasked cells, but the curve fit will not be updated.