convert S4 to S3; add some extra methods to DMatrix

R-package/man/slice.xgb.DMatrix.Rd

@@ -0,0 +1,41 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/xgb.DMatrix.R
+\name{slice}
+\alias{[.xgb.DMatrix}
+\alias{slice}
+\alias{slice.xgb.DMatrix}
+\title{Get a new DMatrix containing the specified rows of
+orginal xgb.DMatrix object}
+\usage{
+slice(object, ...)
+
+\method{slice}{xgb.DMatrix}(object, idxset, ...)
+
+\method{[}{xgb.DMatrix}(object, idxset, colset = NULL)
+}
+\arguments{
+\item{object}{Object of class "xgb.DMatrix"}
+
+\item{...}{other parameters (currently not used)}
+
+\item{idxset}{a integer vector of indices of rows needed}
+
+\item{colset}{currently not used (columns subsetting is not available)}
+}
+\description{
+Get a new DMatrix containing the specified rows of
+orginal xgb.DMatrix object
+}
+\examples{
+data(agaricus.train, package='xgboost')
+train <- agaricus.train
+dtrain <- xgb.DMatrix(train$data, label=train$label)
+
+dsub <- slice(dtrain, 1:42)
+labels1 <- getinfo(dsub, 'label')
+dsub <- dtrain[1:42, ]
+labels2 <- getinfo(dsub, 'label')
+all.equal(labels1, labels2)
+
+}
+