b4d97d3cb8
* [R] better argument check in xgb.DMatrix; fixes #1480 * [R] showsd was a dummy; fixes #2044 * [R] better categorical encoding explanation in vignette; fixes #1989 * [R] new roxygen version docs update
38 lines
1.7 KiB
R
38 lines
1.7 KiB
R
% Generated by roxygen2: do not edit by hand
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% Please edit documentation in R/callbacks.R
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\name{callbacks}
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\alias{callbacks}
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\title{Callback closures for booster training.}
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\description{
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These are used to perform various service tasks either during boosting iterations or at the end.
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This approach helps to modularize many of such tasks without bloating the main training methods,
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and it offers .
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}
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\details{
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By default, a callback function is run after each boosting iteration.
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An R-attribute \code{is_pre_iteration} could be set for a callback to define a pre-iteration function.
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When a callback function has \code{finalize} parameter, its finalizer part will also be run after
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the boosting is completed.
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WARNING: side-effects!!! Be aware that these callback functions access and modify things in
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the environment from which they are called from, which is a fairly uncommon thing to do in R.
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To write a custom callback closure, make sure you first understand the main concepts about R envoronments.
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Check either R documentation on \code{\link[base]{environment}} or the
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\href{http://adv-r.had.co.nz/Environments.html}{Environments chapter} from the "Advanced R"
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book by Hadley Wickham. Further, the best option is to read the code of some of the existing callbacks -
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choose ones that do something similar to what you want to achieve. Also, you would need to get familiar
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with the objects available inside of the \code{xgb.train} and \code{xgb.cv} internal environments.
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}
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\seealso{
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\code{\link{cb.print.evaluation}},
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\code{\link{cb.evaluation.log}},
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\code{\link{cb.reset.parameters}},
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\code{\link{cb.early.stop}},
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\code{\link{cb.save.model}},
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\code{\link{cb.cv.predict}},
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\code{\link{xgb.train}},
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\code{\link{xgb.cv}}
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}
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