I recently discovered a powerful use for R expression()’sSay you are trying to fit some experimental data to the following nonlinear equation: Ky0eu(x−tl)K+y0(eu∗(x−tl)−1)+b1+(b0−b1)e−kx+b2x with the independent variable x using nlminb() as the minimization optimizer.This sort of work is significantly improved (i.e. faster with better convergence) if an analytical gradient vector and a Hessian matrix for the objective function are provided....