I'm using elki with the gui and the command line and I want to use the Optics Xi algorithm with the same minPts value but different Xi values multiple times. So as far as I understand Optics Xi it should not be necessary to run the normal Optics algorithm more than once to calculate the clusters with different Xi parameters. Is there a way to reuse the reachability distances from Optics for the Optics Xi calculations in elki?
Not on command line / MiniGUI as of now. OPTICSXi is implemented as a wrapper around an OPTICSTypeAlgorithm, because then people don't forget to first run OPTICS, before adding OPTICSXi
But this is trivial to do using the source code, since OPTICSXi does not change the OPTICS result. Just make the extractClusters method public and call it on the existing ClusterOrder.
To make this possible to use from command line / MiniGUI, you could do a stub OPTICSTypeAlgorithm algorithm that simply "reuses" an existing OPTICS cluster order.