After you have manually picked, or automatically traced points on a curve, you may not be happy with the difference in X intervals between the data points. In this case you can resample the data to have constant (ln-) X intervals by pressing Ctrl+J or choosing Resample data from the Data menu.
The data will automatically be sorted in increasing X direction, if that is not yet done. Make sure there is only a single Y value for each X value if you use this function; resample expect a functional dependence of Y on X data.
You will be prompted for the number of points in the X direction after resampling. The default interval is the current number of points in the data set. The minimum and maximum X-values will also be taken from the data points in the current set.
By default, your point will be resampled using linear interpolation. Cubic spline interpolation is also available and can be selected from the Options menu. This may suffer from overshoots. If you experience this, you can change the interpolation method back to linear interpolation.
See also: Manipulating data.