Relations of rotational and cycle periods vs. T_eff. Stars with simple cycles are plotted with red dots, stars with complex cycles with blue squares, and the Sun with an orange star. The components of the wide binaries HD 131156A/B and HD 201091/HD 201092 are connected. Top: rotational periods versus effective temperatures. Bottom: P_cyc/P_rot (related to the dynamo number) versus effective temperature. The fit for the stars with complex cycles shows a relation increasing toward hotter temperatures.