Define the rounding operator associated with the floor function. The function
also returns zero whenever the input is negative and caps the value at y_max,
where y_max is a known upper bound on the data y (if specified).
Define the rounding operator associated with the floor function. The function
also returns zero whenever the input is negative and caps the value at y_max,
where y_max is a known upper bound on the data y (if specified).