# ml_decision_tree_classifier

##### Spark ML -- Decision Trees

Perform classification and regression using decision trees.

##### Usage

```
ml_decision_tree_classifier(x, formula = NULL, max_depth = 5L,
max_bins = 32L, min_instances_per_node = 1L, min_info_gain = 0,
impurity = "gini", seed = NULL, thresholds = NULL,
cache_node_ids = FALSE, checkpoint_interval = 10L,
max_memory_in_mb = 256L, features_col = "features", label_col = "label",
prediction_col = "prediction", probability_col = "probability",
raw_prediction_col = "rawPrediction",
uid = random_string("decision_tree_classifier_"), ...)
```ml_decision_tree(x, formula = NULL, type = c("auto", "regression",
"classification"), features_col = "features", label_col = "label",
prediction_col = "prediction", variance_col = NULL,
probability_col = "probability", raw_prediction_col = "rawPrediction",
checkpoint_interval = 10L, impurity = "auto", max_bins = 32L,
max_depth = 5L, min_info_gain = 0, min_instances_per_node = 1L,
seed = NULL, thresholds = NULL, cache_node_ids = FALSE,
max_memory_in_mb = 256L, uid = random_string("decision_tree_"),
response = NULL, features = NULL, ...)

ml_decision_tree_regressor(x, formula = NULL, max_depth = 5L,
max_bins = 32L, min_instances_per_node = 1L, min_info_gain = 0,
impurity = "variance", seed = NULL, cache_node_ids = FALSE,
checkpoint_interval = 10L, max_memory_in_mb = 256L, variance_col = NULL,
features_col = "features", label_col = "label",
prediction_col = "prediction",
uid = random_string("decision_tree_regressor_"), ...)

##### 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.- max_depth
Maximum depth of the tree (>= 0); that is, the maximum number of nodes separating any leaves from the root of the tree.

- max_bins
The maximum number of bins used for discretizing continuous features and for choosing how to split on features at each node. More bins give higher granularity.

- min_instances_per_node
Minimum number of instances each child must have after split.

- min_info_gain
Minimum information gain for a split to be considered at a tree node. Should be >= 0, defaults to 0.

- impurity
Criterion used for information gain calculation. Supported: "entropy" and "gini" (default) for classification and "variance" (default) for regression. For

`ml_decision_tree`

, setting`"auto"`

will default to the appropriate criterion based on model type.- seed
Seed for random numbers.

- 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.- cache_node_ids
If

`FALSE`

, the algorithm will pass trees to executors to match instances with nodes. If`TRUE`

, the algorithm will cache node IDs for each instance. Caching can speed up training of deeper trees. Defaults to`FALSE`

.- checkpoint_interval
Set checkpoint interval (>= 1) or disable checkpoint (-1). E.g. 10 means that the cache will get checkpointed every 10 iterations, defaults to 10.

- max_memory_in_mb
Maximum memory in MB allocated to histogram aggregation. If too small, then 1 node will be split per iteration, and its aggregates may exceed this size. Defaults to 256.

- 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.

- type
The type of model to fit.

`"regression"`

treats the response as a continuous variable, while`"classification"`

treats the response as a categorical variable. When`"auto"`

is used, the model type is inferred based on the response variable type -- if it is a numeric type, then regression is used; classification otherwise.- variance_col
(Optional) Column name for the biased sample variance of prediction.

- response
(Deprecated) The name of the response column (as a length-one character vector.)

- features
(Deprecated) The name of features (terms) to use for the model fit.

##### Details

When `x`

is a `tbl_spark`

and `formula`

(alternatively, `response`

and `features`

) is specified, the function returns a `ml_model`

object wrapping a `ml_pipeline_model`

which contains data pre-processing transformers, the ML predictor, and, for classification models, a post-processing transformer that converts predictions into class labels. For classification, an optional argument `predicted_label_col`

(defaults to `"predicted_label"`

) can be used to specify the name of the predicted label column. In addition to the fitted `ml_pipeline_model`

, `ml_model`

objects also contain a `ml_pipeline`

object where the ML predictor stage is an estimator ready to be fit against data. This is utilized by `ml_save`

with `type = "pipeline"`

to faciliate model refresh workflows.

`ml_decision_tree`

is a wrapper around `ml_decision_tree_regressor.tbl_spark`

and `ml_decision_tree_classifier.tbl_spark`

and calls the appropriate method based on model type.

##### Value

The object returned depends on the class of `x`

.

`spark_connection`

: When`x`

is a`spark_connection`

, the function returns an instance of a`ml_predictor`

object. The object contains a pointer to a Spark`Predictor`

object and can be used to compose`Pipeline`

objects.`ml_pipeline`

: When`x`

is a`ml_pipeline`

, the function returns a`ml_pipeline`

with the predictor appended to the pipeline.`tbl_spark`

: When`x`

is a`tbl_spark`

, a predictor is constructed then immediately fit with the input`tbl_spark`

, returning a prediction model.`tbl_spark`

, with`formula`

: specified When`formula`

is specified, the input`tbl_spark`

is first transformed using a`RFormula`

transformer before being fit by the predictor. The object returned in this case is a`ml_model`

which is a wrapper of a`ml_pipeline_model`

.

##### See Also

See http://spark.apache.org/docs/latest/ml-classification-regression.html for more information on the set of supervised learning algorithms.

Other ml algorithms: `ml_aft_survival_regression`

,
`ml_gbt_classifier`

,
`ml_generalized_linear_regression`

,
`ml_isotonic_regression`

,
`ml_linear_regression`

,
`ml_linear_svc`

,
`ml_logistic_regression`

,
`ml_multilayer_perceptron_classifier`

,
`ml_naive_bayes`

,
`ml_one_vs_rest`

,
`ml_random_forest_classifier`

##### Examples

```
# NOT RUN {
sc <- spark_connect(master = "local")
iris_tbl <- sdf_copy_to(sc, iris, name = "iris_tbl", overwrite = TRUE)
partitions <- iris_tbl %>%
sdf_partition(training = 0.7, test = 0.3, seed = 1111)
iris_training <- partitions$training
iris_test <- partitions$test
dt_model <- iris_training %>%
ml_decision_tree(Species ~ .)
pred <- sdf_predict(iris_test, dt_model)
ml_multiclass_classification_evaluator(pred)
# }
# NOT RUN {
# }
```

*Documentation reproduced from package sparklyr, version 0.8.4, License: Apache License 2.0 | file LICENSE*