Hardness-intensity diagram for all MAXI observations during the time period from 2009 to 2018 for Cyg X-1. Photon counts in the energy band 2–10 keV are approximated by counts in the band 2–20 keV minus counts in 10–20 keV. The hardness ratio is defined as counts in the energy bands 4–10 keV vs. 2–4 keV. The blue vertical line indicates the threshold of h = 0.45. Two red error bars indicate the errors at higher and lower photon count rates.