PROBLEM TO BE SOLVED: To predict changes in the state of living organisms and to enable control.SOLUTION: An expression level of molecules in a living organism is measured at specific time intervals, the measured time series data is divided into periodic components, response to environmental stimuli components, and base line components. Constant regions of the time series data is identified from fluctuations in the base line components, the amplitude of periodic components or fluctuations in the period, and a causal relationship between the identified constant regions is identified. A relationship between fluctuations in the internal environment and the external environment is identified, and from the causal relationship between the identified constant regions, changes in the state of the living organisms are inferred. Furthermore, from the relationship between fluctuations in the internal environment and the external environment, the onset of a disease in the living organism can be inferred. The molecules can be molecules in the blood or molecules in the culture medium.SELECTED DRAWING: Figure 2
