If cobra$TrustRegion==TRUE (see cobraInit), then the trustRegion functionality is applied
every iteration in order to refine the best solution so far.
This function builds a local model around the best solution and runs a local search in the trust region
to refine the best solution and find a better solution in the neighborhood.
trustRegion(cobra, center = cobra$xbest)an object of class cobra, which is basically a list (see cobraInit)
[cobra$xbest] the center of the trust region
the modified cobra with new/updated elements
logical, is TRUE if there are more than d+1 points in the trusted
region and thus surrogates can be trained. Otherwise FALSE.
if TRDONE==TRUE the refined solution from the trust-region call,
otherwise NA