1. A computer-implemented method for scaling a circuit behavior x in a library set to a desired operating point P′ that is defined by a set of operating conditions p j ′, the library set containing values x(n) for the circuit behavior characterized at characterization points P(n), each characterization point P(n) defined by a set of operating conditions p j (n), the method comprising the steps of: estimating G(n) −1 by: applying a nonlinear transform to each characterization point P(n) to obtain Q(n), a nonlinear transform of the characterization point P(n); and calculating G(n) −1 from Q(n) based on a parameterized model for y of the form y=G T B, where y is a transform of the circuit behavior x, G is a vector of the functional forms of each term in the parameterized model as a function of components q k of Q, B is a vector of the corresponding coefficients for each functional form, and G(n) is a matrix containing G at different characterization points P(n); and for the desired operating point P′: applying the nonlinear transform to P′ to calculate Q′; applying the functional forms of the parameterized model to Q′ to calculate G′; calculating y′=G′ T G(n) −1 y(n); and applying an inverse of the transform to y′ to estimate x′, the estimated circuit behavior at operating point P′.