If D were the driving factor, it would be possible to express expected energy consumption E mathematically as:
E = k0 + k1Dn ---(1)
and this could be represented graphically, although the characteristic line would be curved rather than straight. This is not a major problem, except that not many M&T software systems would have provision to accommodate such a case. A straight line is preferable in that respect. To force the graph to look like a straight line, one can manipulate D, and create a 'transformed' version of the driving factor, D', thus:
D' = Dn
which transforms equation (1) into the familiar straight-line model:
E = k0 + k1D'
It is not just simple clean curves which can be transormed in this fashion. Quite complex discontinuous functions could also be tamed in an analogous way.