The sfcr_set_index() function takes a list of equations as its input and returns
a tibble containing the name of the variable on the left-hand side of the equations
and their position in the equations list.
sfcr_set_index(eqs)A list of equations created with sfcr_set()
This function aims to facilitate locating a specific equation in the list in order to modify the list of equations.
To add random variation to endogenous variables, use sfcr_random().