This family is the equivalent, in terms of levels, of the Interpolated and Curve Fitted Rates family, the latter of which could be considered as the integral (area under the curve) of the former.

This family is for when you have a number of levels at various points in time and you need to be able to project inbetween them, say for a forecast of prices.

The two ways of projecting using an input range of data points correspond to the two functions in this family:

• The InterpedLevel function uses interpolation to estimate values inbetween the points. The levels at the points themselves are honoured exactly. Inbetween, you can use linear, cubic or other interpolation methods.
  
  
• The FittedLevel takes a different approach, and does not guarantee that it will exactly honour each point (in fact, it almost definetely won't). Instead it will fit a smooth polynomial curve to the data, either to an order of polynomial you specify, or it will find the best one and use that.