This command selects the downhill simplex method to minimize the objective function. The downhill simplex method does not calculate derivatives and can therefore be used for discontinuous objective functions. The initial simplex is defined by the initial parameter set p0 and n additional points given by :
pi = p0 + sigmai * ei i=2,…,(n+1)where sigma is the parameter variation given by commands >>>> VARIATION or >>>> DEVIATION (p), and the e‘s are n unit vectors along the parameter axis. At the end of minimization by means of the simplex algorithm, the Jacobian matrix is evaluated to allow for a standard error analysis. The simplex algorithm is most useful in connection with the L1-estimator and discontinuous cost functions.
>>> use SIMPLEX algorithm to minimize objective function