IRFs starting from period 0/1


Dear community,

in the model I am building, some IRFs start in period one at some value, others in period zero at the steady state and others in period zero at some value different from the steady state. The second and third case are standard, it is the first one that puzzles me:

How can an IRF start in period one without having a line drawn from the steady state level in period zero?

I just could not think of any reason for that. I appreciate any hints on this probably easy matter.


I would need to see an example of this.