Relation between the observed rotational and cycle periods. Stars with simple cycles are plotted with red dots, stars with complex cycles with blue squares, and the Sun with orange stars (Gleissberg, Schwabe, and 3–4 yr cycles). Small black squares denote additional cycles, and small green dots are the results from Oláh et al. (2009). The fit is only done for the dominant cycles derived in this paper. It traverses the region of the fast-rotating K-dwarf stars (singles and binaries) in the sample of Oláh et al. (2009). See the text for further discussion.