PLS-POS: Pre-segmentation setting

[janschreier]

Hi smartPLS-team,

what is the reasoning behind the pre-segmentation option? Is it to reduce calculation time but at the same time increasing the risk to getting stuck in a local optimum?

Thanks for your support!
Jan

[jmbecker]

Yes, more or less this is a good summary.
With the pre-segmentation, in the first round all observations are switched to the group where they have the minimum distance. Later in the algorithm, we only switch one observation at a time. The reason is that switching to many observations at a time (like in PLS-REBUS) leads to very unstable groups and therefore imperfect assignments. In the first round, however, it might give the algorithm a boost in terms of avoiding some otherwise necessary iterations.

[janschreier]

Thank you for the answer, Jan-Michael!
Do you have or know of any empirical tests of this pre-segmentation that give some rules of thumb if one should use it or not?

[jmbecker]

From our simulation work when we evaluated the method we usually used it because it didn't reduced quality of the results, but improved performance.

[janschreier]

Thanks again!