List of parameters

a lgb.Dataset object, used for training. Some functions, such as lgb.cv, may allow you to pass other types of data like matrix and then separately supply label as a keyword argument.

number of training rounds

a list of lgb.Dataset objects, used for validation

objective function, can be character or custom objective function. Examples include regression, regression_l1, huber, binary, lambdarank, multiclass, multiclass

evaluation function(s). This can be a character vector, function, or list with a mixture of strings and functions.

• a. character vector: If you provide a character vector to this argument, it should contain strings with valid evaluation metrics. See The "metric" section of the documentation for a list of valid metrics.

• b. function: You can provide a custom evaluation function. This should accept the keyword arguments preds and dtrain and should return a named list with three elements:

  • name: A string with the name of the metric, used for printing and storing results.

  • value: A single number indicating the value of the metric for the given predictions and true values

  • higher_better: A boolean indicating whether higher values indicate a better fit. For example, this would be FALSE for metrics like MAE or RMSE.

• c. list: If a list is given, it should only contain character vectors and functions. These should follow the requirements from the descriptions above.

verbosity for output, if <= 0, also will disable the print of evaluation during training

Boolean, TRUE will record iteration message to booster$record_evals

evaluation output frequency, only effect when verbose > 0

path of model file of lgb.Booster object, will continue training from this model

feature names, if not null, will use this to overwrite the names in dataset

list of str or int type int represents index, type str represents feature names

int. Activates early stopping. Requires at least one validation data and one metric. If there's more than one, will check all of them except the training data. Returns the model with (best_iter + early_stopping_rounds). If early stopping occurs, the model will have 'best_iter' field.

List of callback functions that are applied at each iteration.

Boolean, setting it to TRUE (not the default value) will transform the booster model into a predictor model which frees up memory and the original datasets

other parameters, see Parameters.rst for more information. A few key parameters:

• boosting: Boosting type. "gbdt", "rf", "dart" or "goss".

• num_leaves: Maximum number of leaves in one tree.

• max_depth: Limit the max depth for tree model. This is used to deal with overfit when #data is small. Tree still grow by leaf-wise.

• num_threads: Number of threads for LightGBM. For the best speed, set this to the number of real CPU cores, not the number of threads (most CPU using hyper-threading to generate 2 threads per CPU core).