Direct Approximation of a Function or its Inverse
- by far the most efficient approach for a fixed accuracy criterion,
- maximum flexibility in efficiency vs. accuracy tradeoffs,
- can use piecewise approximation for increased efficiency.
- more difficult to include ERM parameters as variables,
- requires non-linear approximation tools to get coefficients,
- requires considerable analyst experience and intuition.
and once the ERM is fixed becomes
where the Ci are constants.