46 lines
1.5 KiB
R
46 lines
1.5 KiB
R
setClass('xgb.DMatrix')
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#' Get a new DMatrix containing the specified rows of
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#' orginal xgb.DMatrix object
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#'
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#' Get a new DMatrix containing the specified rows of
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#' orginal xgb.DMatrix object
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#'
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#' @examples
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#' data(agaricus.train, package='xgboost')
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#' train <- agaricus.train
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#' dtrain <- xgb.DMatrix(train$data, label=train$label)
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#' dsub <- slice(dtrain, 1:3)
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#' @rdname slice
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#' @export
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#'
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slice <- function(object, ...){
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UseMethod("slice")
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}
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#' @param object Object of class "xgb.DMatrix"
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#' @param idxset a integer vector of indices of rows needed
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#' @param ... other parameters
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#' @rdname slice
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#' @method slice xgb.DMatrix
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setMethod("slice", signature = "xgb.DMatrix",
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definition = function(object, idxset, ...) {
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if (class(object) != "xgb.DMatrix") {
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stop("slice: first argument dtrain must be xgb.DMatrix")
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}
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ret <- .Call("XGDMatrixSliceDMatrix_R", object, idxset,
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PACKAGE = "xgboost")
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attr_list <- attributes(object)
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nr <- xgb.numrow(object)
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len <- sapply(attr_list,length)
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ind <- which(len==nr)
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if (length(ind)>0) {
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nms <- names(attr_list)[ind]
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for (i in 1:length(ind)) {
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attr(ret,nms[i]) <- attr(object,nms[i])[idxset]
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}
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}
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return(structure(ret, class = "xgb.DMatrix"))
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})
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