I am confused about the definition of state variables. My understanding is a state variable is determined at the beginning of period t and it will not be changed at this period. I did not find clear explanation from textbooks I read.
When I use the command M_.endo_names(M_.state_var) to see what are state variables in SW2007, it shows y (output), c (consumption) and r (nominal interest rate) are state variables. Should they be control variables?
Could anyone provide some explanation for state variables or some references?