I have a quenstion about comparing models. Not models fitted by R itself, but user defined models. Ill explain through this example:

Dataset:

Tree Diameter Biomass Model1biomass Model2biomass

1 10 50 45 60

2 7 35 52 48

The 'Biomass' column was received by actually cutting the trees and weighing them. The two other colums 'Model1biomass' and 'Model2biomass' were obtained using the following formulas:

Model1biomass = 34.4703-8.0671*Diameter+0.6589*Diameter*Diameter

Model2biomass = 38.49089-11.7883*Diameter+1.1926*Diameter*Diameter

So these equations use the column 'Diameter' to determine the total biomass.

My problem is comparing these results/models with the correct biomass (the values in column 'Biomass') in terms of RSE, AIC...

How can i do that scince these are not fitted models, and or not linear?

Thank you

Wooferd