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 a computer system executing software instructions to effect the steps of: estimating G(n) −1 by: applying a nonlinear transform to each characterization point P(n) to obtain a corresponding Q(n), wherein each Q(n) is a nonlinear transform of the characterization point P(n) and each Q(n) is defined by a set of terms q k (n); and calculating G(n) −1 from Q(n) based on a parameterized model for y(n) of the form y(n)=G(n) T B, where y(n) is a transform of the circuit behavior x(n), each G(n) is a vector of terms g 1 (n), each g 1 (n) is a functional form of a term in the parameterized model as a function of component(s) q k (n) of Q(n), and B is a vector of the corresponding coefficients for each functional form; and for the desired operating point P′: applying the nonlinear transform to P′ to calculate Q′ that corresponds to P′; applying the functional forms of the parameterized model to Q′ to calculate G′ that corresponds to Q′; calculating y′=G′ T G(n) −1 y(n), where T indicates the transpose; and applying an inverse of the transform to y′ to estimate x′, the estimated circuit behavior at operating point P′.