hessian method
Returns H = 2 * Jt•J
Implementation
List<List<double>> hessian(List<double> params) {
List<List<double>> jac = jacobian(params);
List<List<double>> jacTrans = numeric.transpose(jac);
List<List<double>> hes = numeric.dotCM(2.0, numeric.dotMM(jacTrans, jac));
//fixed parameters should have a zero in the hessian
// dim = numeric.dim(hes);
// for (var i=0; i<dim[0]; i++) {
// if (free[i] === 0) {
// hes[i][i] = 0.0;
// }
// }
return hes;
}