mltoptim: Control Optimisation

In mlt: Most Likely Transformations

Control Optimisation

Description

Define optimisers and their control parameters

Usage

mltoptim(
   auglag = list(
        kkt2.check = hessian,         ### turn off/on numerical hessian
               eps = abstol,          ### absolute tolerance for _parameter_ updates
             itmax = 1000L,           ### max number of outer iterations
            method = "BFGS",          ### inner algorithm
             maxit = 500L             ### max number of inner (BFGS) iterations    
        ), 
    spg = list(
              ftol = abstol,          ### absolute tolerance for _neg. logLik_
             quiet = TRUE,            ### don't talk
         checkGrad = FALSE            ### don't check analytical gradient
    ),
    nloptr = list(
         algorithm = "NLOPT_LD_MMA",  ### inner algorithm 
          ftol_rel = reltol,          ### relative change for _neg. logLik_
          ftol_abs = abstol,          ### absolute tolerance for _neg. logLik_
           maxeval = 1000L            ### max number of evaluations
    ),
    constrOptim = list(
            method = "BFGS",          ### inner algorithm       
             maxit = 1000L,           ### max number of inner (BFGS) iterations 
  outer.iterations = 500L,            ### max number of outer iterations
         outer.eps = reltol,          ### relative change for _neg. logLik_          
           hessian = hessian          ### turn off/on numerical hessian
    ),        
    nlminb = list(
  checkconstraints = TRUE,            ### return -Inf if violated
          iter.max = 1000L,           ### max number of iterations 
          eval.max = 1500L,           ### max number of function evaluations
           rel.tol = reltol,          ### relative change for _neg. logLik_
           abs.tol = 0.0,             ### absolute tolerance (nll is not >= 0) 
            xf.tol = 1e-10
    ),  
  abstol = 1e-07, 
  reltol = 1e-6, 
   trace = FALSE, 
 hessian = FALSE) 

Arguments

auglag	A list with control parameters for the auglag optimiser. maxtry is the number of times the algorithm is re-started in case it failed.
spg	A list with control parameters for the BBoptim optimiser (calling spg internally).
nloptr	A list with control parameters for the nloptr family of optimisers.
constrOptim	A list with control parameters for the constrOptim optimiser.
nlminb	A list with control parameters for the nlminb optimiser producing an unconstrained fit.
abstol, reltol	Absolute and relative tolerances used as stopping criterion by various algorithms.
trace	A logical switching trace reports by the optimisers off.
hessian	A logical indicating if a numerically differentiated Hessian matrix be returned.

Details

This function sets-up functions to be called in mlt internally.

Value

A list of functions with arguments theta (starting values), f (log-likelihood), g (scores), h (Hessian), ui and ci (linear inequality constraints). Adding further such functions is a way to add more optimisers to mlt. The first one in this list converging defines the resulting model.

All procedures except nlminb perform constained optimisation. The model is only defined for parameters meeting the constraints. For parameter configurations not meeting the constraints, the resulting log-likelihood is -Inf. This, however, does not mean that unconstraint optimisation will always produce parameter estimates which lead to valid models.

Examples

  ### set-up linear transformation model for conditional
  ### distribution of dist given speed
  dist <- numeric_var("dist", support = c(2.0, 100), bounds = c(0, Inf))
  ctmm <- ctm(response = Bernstein_basis(dist, order = 4, ui = "increasing"),
              shifting = ~ speed, data = cars)

  ### use auglag with kkt2.check = TRUE => the numerically determined
  ### hessian is returned as "optim_hessian" slot
  op <- mltoptim(auglag = list(maxtry = 5, kkt2.check = TRUE))[1]
  mltm <- mlt(ctmm, data = cars, scale = FALSE, optim = op)

  ### compare analytical and numerical hessian
  all.equal(c(Hessian(mltm)), c(mltm$optim_hessian), tol = 1e-4)

mlt documentation built on Sept. 29, 2025, 3 p.m.