data(agaricus.train, package='xgboost')
dtrain <- with(agaricus.train, xgb.DMatrix(data, label = label, nthread = 2))
labels <- getinfo(dtrain, 'label')
setinfo(dtrain, 'label', 1-labels)
labels2 <- getinfo(dtrain, 'label')
stopifnot(all.equal(labels2, 1-labels))
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