For pesistence length calculation first, you need to choose a curve, using the tool Curve selection.

After curve selection, press the button “Add curve to list” .

Then choose (or create) data file with curves.

Press the button “Ok”.

After that, choose other curve, and add it into the data file with list of curves.

For reliable result you need to collect in data file at least 100 curves.

For persistence length calculation go Mathematics→Persistence lenght→Evaluate:

After this operation in the main window will appeare three new windows:

1) with calculated persistence length.

2) with the graph theta² from contour length of the curve

3) with the setup menu of the graph window.

Where Theta is an angle of curvature along the curve, “Maximum curve length” is a limit on the horizintal axes, “Averaging step” is a value of the step averaging.