Replace Missing Values (or Filter) by function

Right now I am learning rapidminer as part of at Emory as part of their program; however, I am already apprechiate how much time cleaning data Rapid Miner Saves.  One thing I would love to do in rapid miner would be to replace missing values (or even filter) based on a function.  What do I mean?

You know how sometimes you can replace a value by the statisical average?  You know its appropriate to do that based on knowing where the data came from (or source of the data). Sometimes especially in science and engineering, we know one attribute (called y) is really based on 1 - 2 other attritubes (called x).... so that the average is infact and equation based on those two attritubes.  For example, average y = x^2.

[Suggestion]  I would like to be able to replace missing values based on function, like y = x^2, since it would be more accurate then simply the stastical average.   I am learning how to do this in R.  Currently, I have not figure out a way to do this, so I was hoping that developers could add this feature of filter/replacing this base on function.  Or is their a way I could create in my own custum operator?

P.S. I can give a real life example where I ran into this problem while trying to take semi-structured and structure exoplanet data and clean it up.  Would you all be interested in me posting that example.