xgboost (version 3.1.2.1)

xgb.attr: Accessors for serializable attributes of a model

Description

These methods allow to manipulate the key-value attribute strings of an XGBoost model.

Usage

xgb.attr(object, name)
xgb.attr(object, name) <- value
xgb.attributes(object)
xgb.attributes(object) <- value

Value

• xgb.attr() returns either a string value of an attribute or NULL if an attribute wasn't stored in a model.

• xgb.attributes() returns a list of all attributes stored in a model or NULL if a model has no stored attributes.

Arguments

object

Object of class xgb.Booster. Will be modified in-place when assigning to it.

name

A non-empty character string specifying which attribute is to be accessed.

value

For xgb.attr<-, a value of an attribute; for xgb.attributes<-, it is a list (or an object coercible to a list) with the names of attributes to set and the elements corresponding to attribute values. Non-character values are converted to character. When an attribute value is not a scalar, only the first index is used. Use NULL to remove an attribute.

Details

The primary purpose of XGBoost model attributes is to store some meta data about the model. Note that they are a separate concept from the object attributes in R. Specifically, they refer to key-value strings that can be attached to an XGBoost model, stored together with the model's binary representation, and accessed later (from R or any other interface). In contrast, any R attribute assigned to an R object of xgb.Booster class would not be saved by xgb.save() because an XGBoost model is an external memory object and its serialization is handled externally. Also, setting an attribute that has the same name as one of XGBoost's parameters wouldn't change the value of that parameter for a model. Use xgb.model.parameters<-() to set or change model parameters.

The xgb.attributes<- setter either updates the existing or adds one or several attributes, but it doesn't delete the other existing attributes.

Important: since this modifies the booster's C object, semantics for assignment here will differ from R's, as any object reference to the same booster will be modified too, while assignment of R attributes through attributes(model)$<attr> <- <value> will follow the usual copy-on-write R semantics (see xgb.copy.Booster() for an example of these behaviors).

Examples

data(agaricus.train, package = "xgboost")
train <- agaricus.train

bst <- xgb.train(
  data = xgb.DMatrix(train$data, label = train$label, nthread = 1),
  nrounds = 2,
  params = xgb.params(
    max_depth = 2,
    nthread = 2,
    objective = "binary:logistic"
  )
)

xgb.attr(bst, "my_attribute") <- "my attribute value"
print(xgb.attr(bst, "my_attribute"))
xgb.attributes(bst) <- list(a = 123, b = "abc")

fname <- file.path(tempdir(), "xgb.ubj")
xgb.save(bst, fname)
bst1 <- xgb.load(fname)
print(xgb.attr(bst1, "my_attribute"))
print(xgb.attributes(bst1))

# deletion:
xgb.attr(bst1, "my_attribute") <- NULL
print(xgb.attributes(bst1))
xgb.attributes(bst1) <- list(a = NULL, b = NULL)
print(xgb.attributes(bst1))