xgboost_classifier

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XGBoost Classifier

XGBoost classifier for Spark.

Usage
xgboost_classifier(x, formula = NULL, eta = 0.3, gamma = 0,
  max_depth = 6, min_child_weight = 1, max_delta_step = 0,
  grow_policy = "depthwise", max_bins = 16, subsample = 1,
  colsample_bytree = 1, colsample_bylevel = 1, lambda = 1,
  alpha = 0, tree_method = "auto", sketch_eps = 0.03,
  scale_pos_weight = 1, sample_type = "uniform",
  normalize_type = "tree", rate_drop = 0, skip_drop = 0,
  lambda_bias = 0, tree_limit = 0, num_round = 1, num_workers = 1,
  nthread = 1, use_external_memory = FALSE, silent = 0,
  custom_obj = NULL, custom_eval = NULL, missing = NaN, seed = 0,
  timeout_request_workers = 30 * 60 * 1000, checkpoint_path = "",
  checkpoint_interval = -1, objective = "multi:softprob",
  base_score = 0.5, train_test_ratio = 1,
  num_early_stopping_rounds = 0, objective_type = "classification",
  eval_metric = NULL, maximize_evaluation_metrics = FALSE,
  num_class = NULL, base_margin_col = NULL, thresholds = NULL,
  weight_col = NULL, features_col = "features", label_col = "label",
  prediction_col = "prediction", probability_col = "probability",
  raw_prediction_col = "rawPrediction",
  uid = random_string("xgboost_classifier_"), ...)
Arguments
x

A spark_connection, ml_pipeline, or a tbl_spark.

formula

Used when x is a tbl_spark. R formula as a character string or a formula. This is used to transform the input dataframe before fitting, see ft_r_formula for details.

eta

Step size shrinkage used in update to prevents overfitting. After each boosting step, we can directly get the weights of new features and eta actually shrinks the feature weights to make the boosting process more conservative. [default=0.3] range: [0,1]

gamma

Minimum loss reduction required to make a further partition on a leaf node of the tree. the larger, the more conservative the algorithm will be. [default=0]

max_depth

Maximum depth of a tree, increase this value will make model more complex / likely to be overfitting. [default=6]

min_child_weight

Minimum sum of instance weight(hessian) needed in a child. If the tree partition step results in a leaf node with the sum of instance weight less than min_child_weight, then the building process will give up further partitioning. In linear regression mode, this simply corresponds to minimum number of instances needed to be in each node. The larger, the more conservative the algorithm will be. [default=1]

max_delta_step

Maximum delta step we allow each tree's weight estimation to be. If the value is set to 0, it means there is no constraint. If it is set to a positive value, it can help making the update step more conservative. Usually this parameter is not needed, but it might help in logistic regression when class is extremely imbalanced. Set it to value of 1-10 might help control the update. [default=0]

grow_policy

Growth policy for fast histogram algorithm.

max_bins

Maximum number of bins in histogram.

subsample

Subsample ratio of the training instance. Setting it to 0.5 means that XGBoost randomly collected half of the data instances to grow trees and this will prevent overfitting. [default=1] range:(0,1]

colsample_bytree

Subsample ratio of columns when constructing each tree. [default=1] range: (0,1]

colsample_bylevel

Subsample ratio of columns for each split, in each level. [default=1] range: (0,1]

lambda

L2 regularization term on weights, increase this value will make model more conservative. [default=1]

alpha

L1 regularization term on weights, increase this value will make model more conservative, defaults to 0.

tree_method

The tree construction algorithm used in XGBoost. options: 'auto', 'exact', 'approx' [default='auto']

sketch_eps

This is only used for approximate greedy algorithm. This roughly translated into O(1 / sketch_eps) number of bins. Compared to directly select number of bins, this comes with theoretical guarantee with sketch accuracy. [default=0.03] range: (0, 1)

scale_pos_weight

Control the balance of positive and negative weights, useful for unbalanced classes. A typical value to consider: sum(negative cases) / sum(positive cases). [default=1]

sample_type

Parameter for Dart booster. Type of sampling algorithm. "uniform": dropped trees are selected uniformly. "weighted": dropped trees are selected in proportion to weight. [default="uniform"]

normalize_type

Parameter of Dart booster. type of normalization algorithm, options: 'tree', 'forest'. [default="tree"]

rate_drop

Parameter of Dart booster. dropout rate. [default=0.0] range: [0.0, 1.0]

skip_drop

Parameter of Dart booster. probability of skip dropout. If a dropout is skipped, new trees are added in the same manner as gbtree. [default=0.0] range: [0.0, 1.0]

lambda_bias

Parameter of linear booster L2 regularization term on bias, default 0 (no L1 reg on bias because it is not important.)

tree_limit

Limit number of trees in the prediction; defaults to 0 (use all trees.)

num_round

The number of rounds for boosting.

num_workers

number of workers used to train xgboost model. Defaults to 1.

nthread

Number of threads used by per worker. Defaults to 1.

use_external_memory

The tree construction algorithm used in XGBoost. options: 'auto', 'exact', 'approx' [default='auto']

silent

0 means printing running messages, 1 means silent mode. default: 0

custom_obj

Customized objective function provided by user. Currently unsupported.

custom_eval

Customized evaluation function provided by user. Currently unsupported.

missing

The value treated as missing. default: Float.NaN

seed

Random seed for the C++ part of XGBoost and train/test splitting.

timeout_request_workers

the maximum time to wait for the job requesting new workers. default: 30 minutes

checkpoint_path

The hdfs folder to load and save checkpoint boosters.

checkpoint_interval

Param for set checkpoint interval (>= 1) or disable checkpoint (-1). E.g. 10 means that the trained model will get checkpointed every 10 iterations. Note: checkpoint_path must also be set if the checkpoint interval is greater than 0.

objective

Specify the learning task and the corresponding learning objective. options: reg:linear, reg:logistic, binary:logistic, binary:logitraw, count:poisson, multi:softmax, multi:softprob, rank:pairwise, reg:gamma. default: reg:linear.

base_score

Param for initial prediction (aka base margin) column name. Defaults to 0.5.

train_test_ratio

Fraction of training points to use for testing.

num_early_stopping_rounds

If non-zero, the training will be stopped after a specified number of consecutive increases in any evaluation metric.

objective_type

The learning objective type of the specified custom objective and eval. Corresponding type will be assigned if custom objective is defined options: regression, classification.

eval_metric

Evaluation metrics for validation data, a default metric will be assigned according to objective(rmse for regression, and error for classification, mean average precision for ranking). options: rmse, mae, logloss, error, merror, mlogloss, auc, aucpr, ndcg, map, gamma-deviance

maximize_evaluation_metrics

Whether to maximize evaluation metrics. Defaults to FALSE (for minization.)

num_class

Number of classes.

base_margin_col

Param for initial prediction (aka base margin) column name.

thresholds

Thresholds in multi-class classification to adjust the probability of predicting each class. Array must have length equal to the number of classes, with values > 0 excepting that at most one value may be 0. The class with largest value p/t is predicted, where p is the original probability of that class and t is the class's threshold.

weight_col

Weight column.

features_col

Features column name, as a length-one character vector. The column should be single vector column of numeric values. Usually this column is output by ft_r_formula.

label_col

Label column name. The column should be a numeric column. Usually this column is output by ft_r_formula.

prediction_col

Prediction column name.

probability_col

Column name for predicted class conditional probabilities.

raw_prediction_col

Raw prediction (a.k.a. confidence) column name.

uid

A character string used to uniquely identify the ML estimator.

...

Optional arguments; see Details.

Aliases
  • xgboost_classifier
Examples
# NOT RUN {
library(sparkxgb)
library(sparklyr)

sc <- spark_connect(master = "local")
iris_tbl <- sdf_copy_to(sc, iris)
xgb_model <- xgboost_classifier(
  iris_tbl, 
  Species ~ .,
  num_class = 3,
  num_round = 50, 
  max_depth = 4
)
# }
Documentation reproduced from package sparkxgb, version 0.1.0, License: Apache License (>= 2.0)

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