深度复制一个Booster对象

创建一个“xgb.Booster”对象的深度复制，使得其中包含的C对象指针将指向一个不同的对象，因此像xgb.attr()这样的函数不会影响被复制的原始对象。

用法

xgb.copy.Booster(model)

参数

model

一个“xgb.Booster”对象。

值

model的深度复制——它在各方面都将是相同的，但是对该复制对象调用的C级函数不会影响model变量。

示例

library(xgboost)

data(mtcars)

y <- mtcars$mpg
x <- mtcars[, -1]

dm <- xgb.DMatrix(x, label = y, nthread = 1)

model <- xgb.train(
  data = dm,
  params = xgb.params(nthread = 1),
  nrounds = 3
)

# Set an arbitrary attribute kept at the C level
xgb.attr(model, "my_attr") <- 100
print(xgb.attr(model, "my_attr"))

# Just assigning to a new variable will not create
# a deep copy - C object pointer is shared, and in-place
# modifications will affect both objects
model_shallow_copy <- model
xgb.attr(model_shallow_copy, "my_attr") <- 333
# 'model' was also affected by this change:
print(xgb.attr(model, "my_attr"))

model_deep_copy <- xgb.copy.Booster(model)
xgb.attr(model_deep_copy, "my_attr") <- 444
# 'model' was NOT affected by this change
# (keeps previous value that was assigned before)
print(xgb.attr(model, "my_attr"))

# Verify that the new object was actually modified
print(xgb.attr(model_deep_copy, "my_attr"))