% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/callbacks.R
\name{cb.early.stop}
\alias{cb.early.stop}
\title{Callback closure to activate the early stopping.}
\usage{
cb.early.stop(stopping_rounds, maximize = FALSE, metric_name = NULL,
  verbose = TRUE)
}
\arguments{
\item{stopping_rounds}{The number of rounds with no improvement in 
the evaluation metric in order to stop the training.}

\item{maximize}{whether to maximize the evaluation metric}

\item{metric_name}{the name of an evaluation column to use as a criteria for early
stopping. If not set, the last column would be used.
Let's say the test data in \code{watchlist} was labelled as \code{dtest}, 
and one wants to use the AUC in test data for early stopping regardless of where 
it is in the \code{watchlist}, then one of the following would need to be set:
\code{metric_name='dtest-auc'} or \code{metric_name='dtest_auc'}.
All dash '-' characters in metric names are considered equivalent to '_'.}

\item{verbose}{whether to print the early stopping information.}
}
\description{
Callback closure to activate the early stopping.
}
\details{
This callback function determines the condition for early stopping 
by setting the \code{stop_condition = TRUE} flag in its calling frame.

The following additional fields are assigned to the model's R object:
\itemize{
\item \code{best_score} the evaluation score at the best iteration
\item \code{best_iteration} at which boosting iteration the best score has occurred (1-based index)
\item \code{best_ntreelimit} to use with the \code{ntreelimit} parameter in \code{predict}.
     It differs from \code{best_iteration} in multiclass or random forest settings.
}

The Same values are also stored as xgb-attributes:
\itemize{
\item \code{best_iteration} is stored as a 0-based iteration index (for interoperability of binary models)
\item \code{best_msg} message string is also stored.
}

At least one data element is required in the evaluation watchlist for early stopping to work.

Callback function expects the following values to be set in its calling frame:
\code{stop_condition},
\code{bst_evaluation},
\code{rank},
\code{bst} (or \code{bst_folds} and \code{basket}),
\code{iteration},
\code{begin_iteration},
\code{end_iteration},
\code{num_parallel_tree}.
}
\seealso{
\code{\link{callbacks}},
\code{\link{xgb.attr}}
}
